Wafer Heating Apparatus and Semiconductor Manufacturing Apparatus

ABSTRACT

A wafer heating apparatus which is capable of quickly cooling by improving the cooling rate of the heater section is provided. 
     The wafer heating apparatus comprises a plate-shaped member having two opposing principal surfaces with one of the principal surfaces serving as a mounting surface to mount a wafer thereon and the other principal surface having a band-shaped resistive heating member formed thereon, power feeder terminals connected to the resistive heating member for supplying electric power to the resistive heating member, a casing provided to cover the power feeder terminals on the other surface of the plate-shaped member and a nozzle of which tip faces the other surface of the plate-shaped member for cooling the plate-shaped member, wherein the position of the tip of the nozzle as projected onto the other surface of the plate-shaped member is located between the bands of the resistive heating member.

FIELD OF THE INVENTION

The present invention relates to a wafer heating apparatus used in themanufacture and inspection of semiconductors, and a semiconductormanufacturing apparatus using the same, for such applications as forminga thin film of semiconductor on a semiconductor wafer or on a liquidcrystal substrate, or forming a resist film by drying and baking aliquid resist applied onto a wafer.

BACKGROUND ART

Semiconductor devices are extremely important products used in diverseproducts ranging from industrial use to home use. A semiconductor chipwhich constitutes the semiconductor device is manufactured by, forexample, forming various circuits on a silicon wafer and cutting thewafer into the chips of predetermined size.

In a semiconductor manufacturing process where various circuits areformed on a silicon wafer, a wafer heating apparatus is used to heat thesemiconductor wafer such as silicon wafer (hereinafter referred tosimply as wafer) when forming a thin film of semiconductor, etching thefilm and baking the resist film.

Conventional semiconductor manufacturing apparatuses can be divided intobatch operation type which heats a plurality of wafers simultaneouslyand sequential operation type which heats the wafers one by one. Thesequential operation type has an advantage that the temperature can becontrolled more accurately, although it can process less wafers at atime. While the use of semiconductor heating apparatuses of the batchoperation type has been predominant in the past, use of semiconductorheating apparatuses of the sequential operation type where the wafersare processed one by one has been increasing as the wafer size increasesfrom 8 inches to 12 inches while wiring of the semiconductor devicesbecomes finer and higher accuracy is required in controlling the waferprocessing temperature.

When the sequential operation type is employed, however, it is requiredto reduce the time taken to process each wafer since the number ofwafers processed at a time decreases. Therefore, there is a strongdemand for the wafer heating apparatus to reduce the time required incooling down as well as in heating. Accordingly in the wafer heatingapparatus, it is a common practice to place a heater section, comprisinga plate-shaped member which has a resistive heating member, in a casingand provide a cooling nozzle in the casing so as to forcibly cool theheater section by supplying a cooling medium from the nozzle (JapaneseUnexamined Patent Publication (Kokai) No. 2003-100818 and JapaneseUnexamined Patent Publication (Kokai) No. 2004-063813).

Recently wafer heating apparatuses made of ceramics are widely used asthe wiring of the semiconductor devices becomes finer and higheraccuracy is required in controlling the wafer processing temperature.

The wafer heating apparatuses made of ceramics are disclosed in, forexample, Japanese Unexamined Patent Publication (Kokai) No. 2001-135684,Japanese Unexamined Patent Publication (Kokai) No. 2001-203156, JapaneseUnexamined Patent Publication (Kokai) No. 2001-313249 and JapaneseUnexamined Patent Publication (Kokai) No. 2002-76102. FIG. 19 shows awafer heating apparatus 171 made of ceramics disclosed in JapaneseUnexamined Patent Publication (Kokai) No. 2001-203156.

The wafer heating apparatus 171 made of ceramics comprises aplate-shaped ceramic member 172 and a casing 179 as the majorcomponents, wherein the plate-shaped ceramic member 172 made of nitrideceramics or carbide ceramics is secured to the opening of the bottomedcasing 179 made of a metal such as aluminum, by means of bolt 180 via aninsulating connecting member 174 made of a resin, of which top surfaceis used as a mounting surface 173 to mount the wafer W thereon, and aresistive heating member 175 having concentric configuration as shown inFIG. 20 is provided on the bottom surface of the plate-shaped ceramicmember 172 thereby forming a heater section.

With this configuration, a cooling medium is injected from a nozzle 182into a space delimited by the plate-shaped ceramic member 172 and thecasing so as to circulate and is discharged through a discharge port183, thereby cooling the heater section.

In order to form a uniform film over the entire surface of the wafer Wor provide uniform heat-reaction condition of the resist film by usingthe wafer heating apparatus 171 made of ceramics of such a constitution,it is important to make the temperature distribution uniform byminimizing the temperature difference across the surface of wafer, andit is necessary to heat and cool down the wafer in a short period oftime. In addition, it is necessary to change the temperature setting ofthe wafer heating apparatus 171 in order to vary the wafer temperature,and it is required to heat the wafer heating apparatus 171 made ofceramics in a short period of time and cool it down in a short period oftime.

Japanese Unexamined Patent Publication (Kokai) No. 2002-83848 disclosesthat disturbance of the flow of the cooling medium can be mitigated bykeeping the surface roughness of the bottom surface of the casing withina predetermined value, and that it is made possible to improve theefficiency of heating and cooling.

Japanese Unexamined Patent Publication (Kokai) No. 2002-100462 disclosesthat heating rate and cooling rate of the wafer can be increased bycontrolling the heat capacity of the wafer heating apparatus 171 made ofceramic to 5000 J/K or less. However, the casing 179 has a heat capacity3.3 times that of plate-shaped ceramic member 173 or more, and the ratioS/V of the surface area S of the casing 179 to the volume V of thecasing 179 is less than 5 (1/cm), and therefore the cooling time cannotbe sufficiently reduced.

Thus it has been taking relatively long time to change the settemperature of heating the wafer with any of the prior art technologies,and there has been a demand for a wafer heating apparatus capable ofchanging the temperature in a shorter period of time.

In the meantime, it has been in practice to decrease the temperaturedifference across the surface of wafer by controlling the distributionof resistance of the resistive heating member 175 having band shape orcontrolling the temperature of the resistive heating member 175 havingband shape separately, and it has been proposed to increase the amountof heat generated from the surrounding area in the case of a structuresusceptible to heat sink.

But any of the proposals have problems that a very complicated structureand complex control are required, and there is a demand for a waferheating apparatus capable of heating with uniform temperaturedistribution with a simple structure.

Moreover, since the wafer heating apparatus 171 is vulnerable to thelight, heat, processing gas and other influences when used in asemiconductor manufacturing apparatus, the resistive heating member 175is required to have durability against oxidization and other attack onthe surface. For this reason, it has been proposed to coat the resistiveheating member 175 with an insulation layer on a part or whole of thesurface thereof, so as to improve the durability of the resistiveheating member 175 (refer to Japanese Unexamined Patent Publication(Kokai) No. 2001-297857).

Since the insulation layer can also serve as a heat insulator for theresistive heating member 175, it may make an obstacle in quickly coolingdown the wafer heating apparatus 171 which has been heated. Therefore,there has been a wafer heating apparatus where surface roughness Ra ofthe insulation layer is controlled in a range from 0.01 to 10 μm in anattempt to improve the cooling effect (refer to Japanese UnexaminedPatent Publication (Kokai) No. 2001-297858).

DISCLOSURE OF THE INVENTION

As described above, the conventional wafer heating apparatus has theproblem of long cooling time. In particular, it has been difficult tocool down the heater section of the wafer heating apparatus, which heatslarge wafers measuring 300 mm or more, in a short period of time.

A wafer heating apparatus having a resistive heating member covered withan insulation layer has such a problem that the resistive heating memberand the insulation layer have low strength of bonding with theplate-shaped member due to the difference in thermal expansioncoefficients of the constituent materials. Upon repetitive cycles ofheating and cooling, or when cooling gas is discharged from the nozzle,such troubles occur as peel-off of the resistive heating member and theinsulation layer or cracks therein.

Therefore, it is not sufficient in protecting the resistive heatingmember 175 to simply form the insulation layer over the area of theresistive heating member 175 provided on the plate-shaped ceramic member172.

An object of the present invention is to provide a wafer heatingapparatus which is capable of quickly cooling by improving the coolingrate of the heater section comprising the plate-shaped member that hasthe resistive heating member, and a semiconductor manufacturingapparatus which uses the same.

Another object of the present invention is to provide a wafer heatingapparatus which is capable of quickly cooling, and has high reliabilitywithout undergoing any deterioration in performance such as peel-off ofthe resistive heating member and the insulation layer or crack whensubjected to repetitive cycles of heating and cooling, or a coolingmedium is discharged.

In order to achieve the object described above, the wafer heatingapparatus of the present invention comprises a plate-shaped memberhaving two opposing principal surfaces with one of the principalsurfaces serving as a mounting surface to mount a wafer thereon and theother principal surface having a band-shaped resistive heating memberformed thereon, power feeder terminals connected to the resistiveheating member for supplying electric power to the resistive heatingmember, a casing provided to cover the power feeder terminals on theother surface of the plate-shaped member and a nozzle of which tip facesthe other surface of the plate-shaped member for cooling theplate-shaped member, wherein the position of the tip of the nozzle asprojected onto the other surface of the plate-shaped member is locatedbetween the bands of the resistive heating member.

The semiconductor manufacturing apparatus is characterized in that it isprovided with the wafer heating apparatus of the present invention.

The wafer heating apparatus of the present invention having theconstitution described above is capable of quickly cooling, since theposition of the tip of the nozzle as projected onto the other surface ofthe plate-shaped member is located between the bands of the resistiveheating member, it is made possible to increase the cooling rate of theheater section of the plate-shaped member.

The present invention also provides the wafer heating apparatus of highreliability which is capable of quickly cooling without undergoing anydeterioration in performance, by forming protrusions and recesses on thesurface of the resistive heating member.

The present invention further provides the wafer heating apparatus ofhigh reliability which is capable of quickly cooling without undergoingany deterioration in performance, by providing the insulation layer witha surface having protrusions and recesses on the resistive heatingmember.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the constitution of the wafer heatingapparatus according to first embodiment of the present invention.

FIG. 2 is an enlarged view showing the relative position of the coolingnozzle and the resistive heating member in the wafer heating apparatusaccording to the first embodiment.

FIG. 3 is a plan view showing the configuration of bands of theresistive heating member formed on the plate-shaped member and thepositions of the tips of nozzles in the wafer heating apparatusaccording to the first embodiment.

FIG. 4 is a diagram showing a variation of the configuration of bands ofthe resistive heating member formed on the plate-shaped member and thepositions of tips of the nozzles in the wafer heating apparatusaccording to the first embodiment.

FIG. 5A is a sectional view showing the constitution of the waferheating apparatus according to second embodiment of the presentinvention.

FIG. 5B is a plan view showing the constitution of the wafer heatingapparatus according to the second embodiment of the present invention.

FIG. 6 is a front view showing the constitution of the resistive heatingmember of the wafer heating apparatus according to the secondembodiment.

FIG. 7A is a diagram showing the resistive heating member zone of thewafer heating apparatus according to the second embodiment.

FIG. 7B is a diagram showing an example of dividing the ring-shapedresistive heating member zone of the wafer heating apparatus accordingto the second embodiment.

FIG. 8 is a sectional view showing the insulation layer and theresistive heating member formed on the plate-shaped member and thepositions of the tips of the nozzles in the wafer heating apparatusaccording to the second embodiment.

FIG. 9A is a sectional view showing the insulation layer that covers theresistive heating member formed on the plate-shaped member and thepositions of the tips of the nozzles in the wafer heating apparatusaccording to the second embodiment.

FIG. 9B is a diagram showing an example of the ring-shaped insulationlayer in the wafer heating apparatus according to the second embodiment.

FIG. 10 is a sectional view showing the insulation layer and theresistive heating member formed on the plate-shaped member and thepositions of the insulation layer that covers the former and the nozzletips in a variation of the wafer heating apparatus according to thesecond embodiment.

FIG. 11 is a partially enlarged perspective view showing the surfacehaving protrusions and recesses of the insulation layer located betweenthe resistive heating members in a preferable example of the secondembodiment.

FIG. 12 is a front view showing the configuration of the resistiveheating member of the heater section in the wafer heating apparatusaccording to a variation of the second embodiment.

FIG. 13 is a sectional view showing the wafer heating apparatusaccording to third embodiment of the present invention.

FIG. 14A is a sectional view in perspective of the plate-shaped memberof the wafer heating apparatus according to third embodiment.

FIG. 14B is a sectional view of the plate-shaped member of the waferheating apparatus according to the third embodiment.

FIG. 15 is a sectional view in perspective of the plate-shaped member ofthe wafer heating apparatus according to the third embodiment.

FIG. 16 is a plan view of the plate-shaped member of the wafer heatingapparatus according to the third embodiment.

FIG. 17 is an enlarged view showing the relative positions of the tipsof the nozzles and the resistive heating member in the wafer heatingapparatus according to Comparative Example.

FIG. 18 is a plan view showing the configuration of the bands of theresistive heating member and the positions of the tips of the nozzles inthe wafer heating apparatus according to Comparative Example.

FIG. 19 is a section view showing an example of the wafer heatingapparatus of the prior art.

FIG. 20 is a front view showing the configuration of the resistiveheating member in the wafer heating apparatus of the prior art.

DESCRIPTION OF REFERENCE NUMERALS

-   W: Semiconductor wafer-   1: Wafer heating apparatus-   2: Plate-shaped member-   3: Mounting surface-   5: Resistive heating member-   6; Power feeder section-   7: Heater section-   8: Elastic member (power feeder section)-   10: Temperature sensor-   11: Power feeder terminal-   12, 14: Insulation layer-   13: Base plate-   15: Wafer support pin-   16: Opening-   17: Elastic member (casing)-   18: Heat insulating member-   19: Casing (support member)-   22: Side wall-   24: Nozzle-   24 a: Nozzle tip-   401, 55, 61: Surface having protrusions and recesses-   41, 56, 62: Protrusion-   42, 57, 63: Recess-   P20: Position of nozzle tip (between bands of resistive heating    member)-   P30: Position of nozzle tip (between a plurality of resistive    heating members)-   AP: Position of nozzle tip (between bands of resistive heating    member)-   55: Surface having protrusions and recesses of resistive heating    member-   56: Protrusion of resistive heating member-   57: Recess of resistive heating member-   60: Insulation layer-   61: Surface having protrusions and recesses of insulation layer-   62: Protrusion of insulation layer-   63: Recess of insulation layer

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will now be describedwith reference to the accompanied drawings.

First Embodiment

FIG. 1 is a sectional view showing the constitution of the wafer heatingapparatus 1 according to the first embodiment of the present invention.The wafer heating apparatus 1 of the first embodiment comprises aplate-shaped member 2 having one of the principal surfaces thereofserving as a mounting surface 3 to mount a wafer W thereon and the otherprincipal surface having a resistive heating member 5 formed thereon,power feeder terminals 11 for supplying electric power to the resistiveheating member 5, cooling nozzle 24 for cooling the plate-shaped member2 and a metal casing 19 which covers the power feeder terminals 11 andsupports the cooling nozzle 24. Power feeder section 6 connected to theresistive heating member 5 is formed on the other principal surface ofthe plate-shaped member 2, and the power feeder terminals 11 areconnected to the power feeder section 6. The plate-shaped member 2 isattached to the casing 19 via a heat insulating member 18. Thus in thefirst embodiment, the heater section 7 is constituted from theplate-shaped member 2 one of the principal surfaces thereof serving as amounting surface 3 to mount a wafer W thereon, the resistive heatingmember 5 and the power feeder section 6.

According to the present invention, the plate-shaped member 2 ispreferably formed from ceramics consisting of silicon carbide oraluminum nitride having high heat conductivity as the main component.

The resistive heating member 5 preferably has a configuration thatallows it to heat the mounting surface 3 uniformly, such as narrow bandsdisposed symmetrically with respect to the center of the plate-shapedmember 2. Specifically, a spiral shape having a center at the center ofthe plate-shaped member 2 (FIG. 3) or a plurality of separate resistiveheating members 5 in concentric circles may be employed.

Alternatively, a plurality of meandering resistive heating members 5 maybe disposed in a symmetrical arrangement with respect to the center ofthe plate-shaped member 2. FIG. 4 shows an example of the resistiveheating member 5 comprising a plurality (4 in FIG. 4) of meanderingportions consisting of straight segments connected by arced sections.Uniformity of heating can be improved further by dividing the resistiveheating member 5 into a plurality of portions.

In the first embodiment, the power feeder section 6 formed from such amaterial as gold, silver, palladium or platinum is connected to theresistive heating member 5, and the power feeder terminals 11 arepressed into contact with the power feeder section 6 via the elasticmember 8 so as to establish electrical continuity. The power feederterminals 11 may also be directly bonded onto the resistive heatingmember 5 by soldering, brazing or the like.

The metal casing 19 has a side wall 22 and a base plate 13, and theplate-shaped member 2 is disposed to oppose the base plate 13 so as tocover the top of the casing 19. The base plate 13 has the power feederterminals 11 for supplying electric power to the power feeder section 6,the nozzle 24 for cooling the plate-shaped member 2 and temperaturesensors 10 for measuring the temperature of the plate-shaped member 2.The base plate 13 also has an opening 16 for discharging the coolinggas.

While the plate-shaped member 2 and the casing 19 are held together bymeans of bolts along the periphery thereof, these members areelastically held together by screwing nuts via the heat insulationmember 18 and the elastic member 17 so that the plate-shaped member 2and the casing 19 will not make direct contact with each other in thefirst embodiment. With this constitution, since the force acting on theplate-shaped member 2 can be absorbed by the elastic member 17 when thecasing 19 deforms due to temperature change, the plate-shaped member 2can be prevented from deforming or warping, thereby preventing thetemperature of the wafer surface from varying from point to point due towarping of the plate-shaped member 2.

The wafer heating apparatus 1 according to the first embodiment of thepresent invention having the constitution described above is capable ofheating the wafer W uniformly when electric power is supplied to theresistive heating member 5 thereby heating the mounting surface 3. Andthe heater section 7 can be quickly cooled down by sending cooling airfrom the nozzle 24 thereto at the same time as the power supply isstopped.

The wafer heating apparatus 1 according to the first embodiment of thepresent invention is characterized in that the position of the tip ofthe nozzle 24 as projected onto the other surface of the plate-shapedmember 2 is located between the bands of the resistive heating member 5when viewed in the direction of blowing from the nozzle.

FIG. 2 is an enlarged view of a part of FIG. 1 (a portion including theplate-shaped member 2, the resistive heating member 5 and the tip 24 aof the nozzle 24) showing the relative positions of the tip 24 a of thecooling nozzle 24 and the resistive heating member. In the wafer heatingapparatus 1 according to the first embodiment, a cooling medium such ascooling air is injected from the nozzle 24 onto the area between theresistive heating members 5, as shown in FIG. 2.

The phrase that the tip of the nozzle 24 is located between theresistive heating members 5 means that the center of the tip of thenozzle 24 faces the surface of the plate-shaped member 2 located betweenthe adjacent portions of the resistive heating member 5 as indicated byreference numeral P20 in FIG. 3. Preferably, the center of the tip ofthe nozzle 24 faces the center between the adjacent portions of theresistive heating member 5. This means that, in the first embodiment,since the surface of the plate-shaped member 2 having a thermalconductivity higher than that of the surface of the resistive heatingmember 5 is located between the adjacent portions of the resistiveheating member 5, the medium discharged from the nozzle 24 directlycools the surface of the plate-shaped member 2. This enables it toefficiently cool the plate-shaped member 2 so as to remove heat from theheater section 7 in a shorter period of time, thereby reducing the timerequired to cooling the heater section 7.

In case the resistive heating member 5 of the wafer heating apparatus 1according to the first embodiment comprises a plurality of separateportions, the tip of the nozzle 24 may also be disposed so as to facethe surface of the plate-shaped member 2 located between two adjacentportions of the resistive heating member 5.

FIG. 4 is a plan view showing an example of the configuration of theheater section 7 including a plurality of the independent resistiveheating members 5. When the tip 12 a of the cooling nozzle 24 is causedto face the position P30 located between the plurality of the resistiveheating members 5 in the heater section 7 having the constitutiondescribed above, the cooling medium discharged from the nozzle 24directly hits the surface of the plate-shaped member 2 which has highheat conductivity, so as to remove heat from the plate-shaped member 2,thereby enabling it to efficiently cool the heater section 7.

Particularly in the area between the adjacent portions of the resistiveheating member 5, in comparison to the area between the adjacent bandsof the single resistive heating member 5, a larger surface area can besecured for the portion where the medium discharged from the nozzle 24directly hits, so as to make it possible to efficiently cool the heatersection 7 in a short period of time. It is preferable to apply thecooling medium to the area between the plurality of separate portions ofthe single resistive heating member 5 in this way, since it enables itto secure a larger surface area where the cooling medium is caused todirectly hit the plate-shaped member 2.

In the constitution shown in FIG. 4, one piece of inner resistiveheating member 5 having spiral shape is disposed at the center,intermediate resistive heating member 5 having spiral shape is disposedoutside of the former with the centers located at the same position(coaxial arrangement), and four outer resistive heating members 5 aredisposed outside of the former symmetrically with respect to the centerof the plate-shaped member 2 (symmetrical arrangement). That is, in theconstitution shown in FIG. 4, the resistive heating members 5 aredisposed in an arrangement which combines concentricity and symmetrywith the centers of concentricity and symmetry located at the center ofthe plate-shaped member 2, thereby making it possible to decrease thetemperature difference across the surface of wafer and increase thespace S between the resistive heating members 5, so that the exposedarea of the plate-shaped member 2 can be increased and the heatersection 7 can be cooled down efficiently.

While coaxial arrangement and symmetrical arrangement are combined inthe constitution shown in FIG. 4, a plurality of resistive heatingmembers may be disposed in symmetrical arrangement or a plurality ofresistive heating members may be disposed in concentric arrangementaccording to the present invention.

In the wafer heating apparatus 1 according to the first embodiment, itis preferable that the plate-shaped member 2 and the resistive heatingmember 5 have different values of heat conductivity and that heatconductivity of the plate-shaped member 2 is higher than that of theresistive heating member 5.

In the first embodiment, the plate-shaped member 2 is preferably made ofa material having high heat conductivity in the portion which receivesthe flow of cooling medium in order to efficiently cool the plate-shapedmember 2. For this reason, the plate-shaped member 2 is required to havehigh heat conductivity in the portion which receives the flow of coolingmedium, and is set higher than that of the resistive heating member 5 inthe first embodiment. Also in the first embodiment, the resistiveheating member 5 may be formed by printing and baking an electricallyconductive paste that includes electrically conductive metal particles,glass frit and metal oxide, with the resultant material having heatconductivity of 1 to 40 W/(m·K), as will be described in detail later.According to the present invention, it is preferable to use theplate-shaped member 2 having higher heat conductivity. The plate-shapedmember 2 may be made of, for example, sintered aluminum nitride (heatconductivity 180 W/(m·K)) or sintered silicon carbide (heat conductivity100 W/(m·K)).

In the wafer heating apparatus 1 according to the first embodiment, incase a plurality of the nozzles 24 are provided, the plurality ofnozzles 24 are preferably disposed so that the tips of the nozzles 24lie on a circle having the center located at the center of theplate-shaped member 2. That is, it is preferable that positions of thetips of the nozzles as projected onto the other surface of theplate-shaped member 2 lie on a circle when viewed in the direction ofblowing from the nozzle. In case the resistive heating members 5 aredisposed on a circle, it is preferable that this circle and the circlewhereon the tips of the nozzles 24 lie do not coincide with each otheron the plane of projection (the other surface of the plate-shaped member2).

Constitution of the resistive heating member 5 is very important foruniformly heating the wafer. In order to uniformly heat the wafer, it ispreferable that the resistive heating member 5 is disposed in a patternwhich is symmetric with respect to the center of the plate-shaped member2. In case the resistive heating members 5 of arc shape are located onone or more circles, it is preferable that resistance per unit area isconstant along the circle, which enables it to achieve uniformtemperature distribution. When the tips of the nozzles lie on the circlewhere the resistive heating members 5 having arc shape are located insuch a casing, it becomes necessary to dispose the resistive heatingmember 5 so as to avoid this in the nozzle 24 portion, thus resulting indifference in the value of resistance per unit area along the circlewhich causes non-uniform temperature distribution.

For this reason, it is preferable that positions of the centers of thetips of the plurality of nozzles 24 as projected onto the other surfaceof the plate-shaped member 2 lie on a circle different from the circlewhere the resistive heating members 5 having arc shape are located, whenviewed in the direction of blowing from the nozzle.

The number of the nozzles 24 is preferably from 4 to 16. When the numberof the nozzles 24 is less than 4, each nozzle covers too large an areahaving too large heat capacity to cool, thus resulting in low coolingefficiency and longer time taken to cool. When the number of the nozzles24 is more than 16, a large facility having a large capacity of holdinggas is required to obtain sufficient levels of gas pressure and velocityrequired by the nozzle 24, which is not convenient for mass production.Accordingly, the number of the nozzles 24 is preferably from 4 to 16.

It is also preferable that the nozzles 24 are disposed on concentriccircles. When the nozzles are not disposed on concentric circles,cooling effect tends to become uneven such that a longer time is takenin cooling some portions with lower cooling efficiency. In order to coolquickly, it is preferable to dispose the nozzles at symmetricalpositions, which reduces the time taken in cooling and enables efficientcooling operation.

In the wafer heating apparatus 1 according to the first embodiment,temperature of the plate-shaped member 2 is measured by means oftemperature sensor 10 of which distal end is embedded in theplate-shaped ceramic member 2. While the temperature sensor 10 ispreferably sheathed type thermocouple having outer diameter of 0.8 mm orless, in consideration of the response characteristic and the ease ofmaintenance, thermocouple of bare wire type having outer diameter of 0.5mm or less or a thermistor such RTD may also be used. The distal end ofthe temperature sensor 10 is preferably secured in a hole formed in theplate-shaped member 2 while being pressed against the inner wall surfaceof the hole by means of a fastening member provided in the hole, inorder to ensure the reliability of measurement.

Second Embodiment

The wafer heating apparatus according to second embodiment of thepresent invention will now be described with reference to theaccompanying drawings.

FIG. 5A is a sectional view showing the constitution of the waferheating apparatus according to the second embodiment of the presentinvention, and FIG. 5B is a top view thereof.

The wafer heating apparatus 1 of the second embodiment comprises theplate-shaped member 2, having one of the principal surfaces thereofserving as the mounting surface 3 to mount a wafer W thereon and theother principal surface having the band-shaped resistive heating member5 formed thereon via the insulation layer 14, and the casing 19 havingthe opening 16, with the power feeder terminals 11 connected to thepower feeder section 6, the cooling nozzle 24 and pin guide 28 havingthrough hole provided in the casing 19. In the wafer heating apparatus 1of the second embodiment, the heater section 7 is constituted from theplate-shaped member 2, the insulation layer 14, the resistive heatingmember 5 formed thereon and the power feeder sections 6 formed at bothends thereof. The plate-shaped member 2 is formed from, for example,ceramics consisting of silicon carbide or aluminum nitride having a highheat conductivity as the main component. The insulation layer 14 isformed from, for example, an insulating material such as glass or resinwhich can bond well with the plate-shaped member 2. The plate-shapedmember 2 is fastened onto the casing 19 via the heat insulating member18 by means of screws 40 or the like.

A wafer lift pin 25 is inserted into a through hole of the pin guide 28attached to the casing 19 and into a through hole of the plate-shapedmember 2 formed coaxially with the through hole of the pin guide 28, soas to move the wafer W vertically. This enables it to load the wafer Wonto the mounting surface 3 or unload it therefrom.

FIG. 6 is a front view showing the configuration of the resistiveheating member 5 in the wafer heating apparatus of the secondembodiment. In the second embodiment, the resistive heating member 5comprises a plurality of separate portions of resistive heating member 5a, 5 b, 5 c, 5 d, 5 e, 5 f, 5 g, 5 h, and the portions of resistiveheating member 5 a through 5 h are disposed in the correspondingresistive heating member zones 4 a through 4 h. FIGS. 7A, 7B show thedivided resistive heating member zone 4 wherein the portions of theresistive heating member 5 a through 5 h, respectively, are placed.

In the second embodiment, the portions of the resistive heating member 5a, 5 b, 5 c, 5 d, 5 e, 5 f, 5 g, 5 h are formed in narrow consecutiveband, each comprising a first arced section 51 of substantially the samewidth along an arc having center located at the center of theplate-shaped member 2 and a substantially semicircle-shaped band(linkage portion) 52 which connects the first arced sections 51. Thatis, the portions of the resistive heating member 5 a, 5 b, 5 c, 5 d, 5e, 5 f, 5 g, 5 h each consists of a long bending resistive heatingmember formed in meandering shape where the first arced sections 51 isturned back 180 degrees in the turn-back section 52, with the powerfeeder sections 6 provided on both ends. The meandering portions ofresistive heating member 5 a through 5 h are disposed in thecorresponding resistive heating member zones 4 a through 4 h. The powerfeeder sections 6 may not be disposed in the resistive heating memberzone 4 a through 4 h. In the second embodiment, the turn-back section 52is formed as a second arced section having a radius of curvaturesufficiently smaller than that of the first arced section 51, as shownin FIG. 6.

The resistive heating member zone in the wafer heating apparatus of thesecond embodiment is defined as follows.

The resistive heating member zone 4 a is defined as the area inside ofthe circle circumscribing the first arced section 51 which is theoutermost portion of the resistive heating member 5 a.

The resistive heating member zone 4 b is defined as the area between thecircle circumscribing the first arced section 51 which is the outermostportion of the resistive heating member 5 a and the circle inscribingthe first arced section 51 which is located at the innermost position.

The resistive heating member zone 4 cd is defined as the area betweenthe circle circumscribing the first arced section 51 which is theoutermost portion of the resistive heating member 5 c and the resistiveheating member 5 d and the circle inscribing the first arced section 51which is located at the innermost position.

The resistive heating member zone 4 cd is divided into resistive heatingmember zone 4 c and resistive heating member zone 4 d with center angleof 180 degrees, where the resistive heating member 5 c and the resistiveheating member 5 d are formed, respectively.

The resistive heating member zone 4 eh is defined as the area betweenthe circle circumscribing the first arced section 51 which is theoutermost portion of the resistive heating member 5 e and the resistiveheating member 5 h and the circle inscribing the first arced section 51which is located at the innermost position.

The resistive heating member zone 4 eh is divided into four portions ofresistive heating member zones 4 e, 4 f, 4 g, 4 h with center angle of90 degrees, where the resistive heating members Se through 5 h areformed, respectively.

According to the present invention, heating operation can be controlledindependently in each of the resistive heating member zones 4 a through4 h. The resistive heating member provided in each zone is controlledindependently so as to minimize the temperature difference across thesurface of wafer. In the second embodiment, the resistive heating memberzone 4 a is a circular zone having a predetermined radius with thecenter located at the center of the plate-shaped member 2. The resistiveheating member zones 4 b through 4 h are ring-shaped zones that areinterposed between an inner arc and an outer arc having centercorresponding to the center of the plate-shaped member 2, locatedoutside of the resistive heating member zone 4, or zones made bydividing the ring-shaped zone. The zones 4 a and 4 b may also be asingle continuous circular zone. Thus since heating of the resistiveheating member 5 provided in each resistive heating member zone 4 of thewafer heating apparatus of the second embodiment can be controlledindependently, it is made possible to minimize the temperaturedifference across the surface of wafer. According to the presentinvention, the resistive heating member 5 may also have such aconfiguration as the turn-back portion 52 which connects the first arcedsections 51 is a straight line or a curve instead of an arc.

Formed at the ends of the resistive heating member 5 are power feedersections 6 made of a material such as gold, silver, palladium orplatinum. Connection to an external electric power source can beestablished by pressing the power terminals 11 onto the power feedersection 6 by means of an elastic member. The power terminals 11 may alsobe directly connected to the resistive heating member 5 by soldering,brazing or the like.

The metal casing 19 has the side wall 22 and the base plate 21, and theplate-shaped member 2 is disposed to oppose the base plate 21 so as tocover the top of the casing 19. The base plate 21 has the opening 16formed therein for discharging cooling gas, the power feeder terminals11 connected to the power feeder section 6, the cooling nozzle 24 forcooling the plate-shaped member 2 and the temperature sensor 10 formeasuring the temperature of the heater section 7.

The plate-shaped member 2 and the casing 19 are held together by meansof bolts 40 along the periphery thereof, and these members are heldtogether by screwing nuts via the heat insulation member 18 so that theplate-shaped member 2 and the casing 19 do not direct contact with eachother. In the second embodiment, the heat insulating member 18 havingL-shaped cross section is used so as to surround the plate-shaped member2 on the side face along the periphery with the heat insulating member18.

The wafer heating apparatus according to the second embodiment havingthe constitution described above is capable of heating the wafer Wuniformly when electric power is supplied to the resistive heatingmember 5 thereby heating the mounting surface 3. And the heater section7 can be quickly cooled down by sending cooling gas from the nozzle 24at the same time as the power supply is stopped.

The wafer heating apparatus 1 of the present invention is characterizedin that the position of the tip 24 a of the nozzle 24 as projected ontothe other surface of the plate-shaped member is located between thebands of the resistive heating member 5, more preferably betweenadjacent resistive heating member zones 4. Since the surface between theresistive heating member 5 can easily transfer heat via the insulationlayer 14 to the plate-shaped member 2, and the tip 24 a of the nozzle 24is located between the resistive heating member 5, it is made possibleto apply the cooling gas such as air discharged from the nozzle directlyto the surface of the insulation layer 14 so that heat can betransferred via the surface of the insulation layer 14 from theplate-shaped member 2 efficiently to the cooling gas. As a result, heatcan be removed quickly from the plate-shaped member 2, thereby to cooldown the heater section 7 in a short time.

The resistive heating member 5 preferably has such a configuration asthe plurality of first arced sections 51 that have substantially thesame width throughout its length and are turned back in the linkageportion are disposed substantially concentrically as shown in FIG. 6,which enables it to minimize the temperature difference across thesurface of wafer mounted on the mounting surface 3. It is furtherpreferable that distance L1 of the turn-back portion 52 between theadjacent resistive heating members (for example, between the resistiveheating member 5 g and the resistive heating member 5 h) is smaller thanthe distance L4 of the first arced section 51, since this enables it tomake temperature difference across the surface of wafer further smaller.It is also preferable that distance L3 of the turn-back portion 52 inthe same resistive heating member 5 is smaller than the distance L6 ofthe first arced section 51, since this enables it to make temperaturedifference across the surface of wafer further smaller.

FIG. 8 is an enlarged sectional view showing the tip of one coolingnozzle 24 and the plate-shaped member 2, the insulation layer 14 and theresistive heating member 5 disposed around thereof. As shown in FIG. 8,in the wafer heating apparatus 1 of the second embodiment, the coolinggas such as air discharged from the nozzle 24 hits a space between theresistive heating members 5. The phrase that the tip of the nozzle 24 islocated between the resistive heating member 5 means that the center ofthe tip of the nozzle 24 faces the surface of the plate-shaped member 2located between the adjacent portions of the resistive heating member 5as indicated by reference numeral AP in FIG. 7. Preferably, the centerof the tip of the nozzle 24 faces the center between the adjacentportions of the resistive heating member 5. This means that, in thefirst embodiment, since the surface of the plate-shaped member 2 havinga thermal conductivity higher than that of the surface of the resistiveheating member 5 is located between the adjacent portions of theresistive heating member 5, the medium discharged from the nozzle 24directly cools the surface of the plate-shaped member 2. This enables itto efficiently cool the plate-shaped member 2 so as to remove heat fromthe heater section 7 in a shorter period of time, thereby reducing thetime of cooling the heater section 7.

FIG. 9A is a sectional view (sectional view showing a part of sectionenlarged) showing an example of the second embodiment where aninsulation layer (insulation coverage layer) 12 further on the surfaceof the resistive heating member 5. In this example, the resistiveheating member 5 is formed on the insulation layer 14, and theinsulation layer 12 is formed so as to cover the resistive heatingmember 5. Relative positions of the heater section 7 and the nozzle 24are similar to the case shown in FIG. 8.

When the insulation layer 12 is formed on a part or the entire topsurface of the resistive heating member 5, surface of the resistiveheating member 5 can be protected. Thus the surface of the resistiveheating member 5 will not be damaged or contaminated when the coolinggas flows over the resistive heating member 5, and the chronic changecan be reduced after repetitive cycles of heating and cooling theresistive heating member 5, thereby improving the durability.

More specifically, the resistive heating member 5 is formed from aninsulating material based on glass including electrically conductiveparticles made of a noble metal dispersed therein, and may experiencechronic change if the surface of the resistive heating member 5 isexposed or the resistive heating member 5 may come off due to thermalstrain if the resistive heating member 5 is exposed to the cooling gas,while the insulation layer 12 prevents these troubles from occurring.That is, covering the resistive heating member 5 with the insulationlayer 12 makes it possible to mitigate the occurrence of thermal strainin the resistive heating member 5, so that resistance of any part of theresistive heating member 5 does not change even when the wafer heatingapparatus 1 repeats heating and cooling cycles, thus improving thedurability and heating the surface of the wafer W uniformly. It sufficesto form the insulation layer 12 over an area that can cover theresistive heating member 5. It is preferable that the area covered bythe insulation layer 12 is not larger than necessary. It is preferablethat the insulation layers 12 a, 12 b, 12 cd, 12 eh are independent incorrespondence to the resistive heating member zones 4 a, 4 b, 4 cd and4 eh, as will be described in detail later. The resistive heating memberzone 4 cd is the ring-shaped region that combines the resistive heatingmember zone 4 c and the resistive heating member zone 4 d, and theresistive heating member zone 4 eh is the ring-shaped region thatcombines the resistive heating member zone 4 e, the resistive heatingmember zone 4 f, the resistive heating member zone 4 g and the resistiveheating member zone 4 h.

FIG. 9B is a plan view showing the positional relationship between theplate-shaped member 2, the insulation layers 12 (12 a, 12 b, 12 cd, 12eh) and the tip 24 a of the nozzle 24. According to the secondembodiment, in the wafer heating apparatus 1 having the insulation layer12 which covers the resistive heating member 5, the position of the tip24 a of the nozzle 24 as projected onto the other surface of theplate-shaped member 2 is located between the insulation layers 12(between the insulation layer 12 cd and the insulation layer 12 eh inthe example shown in FIG. 9B), so that the cooling gas such as air blownfrom the nozzle 24 is applied to between the insulation layers 12 thatcover the resistive heating member 5. Since the insulation layer 12 isnot formed at this position, heat of the plate-shaped member 2 can betransferred efficiently through the insulation layer 14. Since thecooling gas discharged from the nozzle 24 directly cools the insulationlayer 14 on the surface of the plate-shaped member 2, so as to enable itto efficiently cool the plate-shaped member 2 and remove heat from theheater section 7 in a shorter period of time, thereby reducing the timeof cooling the heater section 7.

FIG. 10 shows another example where the insulation layer 12 is formed onthe resistive heating member 5. The insulation layer 12 is formed notonly on the top surface of the resistive heating member 5 but also onthe insulation layer 14. Here the portion of the insulation layer 12formed on the insulation layer 14 is called the insulation layer 12 a,and the portion of the insulation layer 12 formed on the resistiveheating member 5 is called the insulation layer 12 b. While the surfaceof the plate-shaped member 2 located between the resistive heatingmember is covered by the insulation layer 12 a or the insulation layer14, it is easier to transfer the heat to the plate-shaped member 2through the insulation layer 12 a than through the insulation layer 12 bformed on the resistive heating member 5. Therefore, the plate-shapedmember 2 can be cooled efficiently when the nozzle 24 is disposed sothat the projected, position of the tip thereof falls at a positionbetween the resistive heating members 5, so as to cause the cooling gasdischarged from the nozzle 24 to cool the insulation layer 12 a betweenthe resistive heating members 5.

FIG. 7A is a schematic diagram showing an example of division of theresistive heating member zone 4 according to the present invention. Theresistive heating member zone 4 is defined in the other principalsurface of the plate-shaped member 2. According to the secondembodiment, it is preferable that the resistive heating member zone 4 aof circular shape is located at the center of the plate-shaped member 2and two or three concentric resistive heating member zones of ring shapeare provided on the outside thereof. In the example shown in FIG. 7A,the resistive heating member zone 4 a, the resistive heating member zone4 cd and the resistive heating member zone 4 eh of concentric circlesare provided on the outside of the resistive heating member zone 4 a.The resistive heating member zone 4 a and the resistive heating memberzone 4 b may be connected into a single resistive heating member zone.

In the second embodiment, in order to improve the uniformity of heatingthe wafer W, it is more preferable to divide the ring-shaped resistiveheating member zone having a relatively large surface area located onthe outside (for example, 4 cd, 4 eh) into 2, 3 or 4 resistive heatingmember zones. The divided configuration will be described later withreference to FIG. 7B. Heating of the surface of the disk-shaped wafer Wis affected by the atmosphere around the wafer W, wall surface opposingthe wafer W and the gas flow. Therefore, it is preferable to design suchthat the atmosphere around the wafer W, wall surface opposing the waferW and the flow of gas become symmetric with respect to the center of thewafer W, in order to minimize the temperature difference across thesurface of wafer. In order to heat the wafer W uniformly, it isnecessary to use the wafer heating apparatus suited to the situationsymmetric with respect to the center of the wafer W. It is preferable toform the resistive heating member zone 4 by dividing the mountingsurface 3 in a configuration symmetric with respect to the center.

In order to uniformly heat the surface of a wafer W measuring 300 mm ormore, in particular, it is preferable to provide the ring-shapedresistive heating member zones in two or more concentric circles.

The wafer heating apparatus 1 having plurality of the resistive heatingmember 5 corresponding to the plurality of ring-shaped resistive heatingmember zones formed in the concentric circles is capable of controllingand correcting the slight deviation from symmetry in the environment andthe variation in thickness of the symmetric heating member individuallyfor each resistive heating member, and therefore the temperaturedifference across the surface of wafer can be decreased further.

FIG. 7B is a plan view showing another example of the resistive heatingmember zone 4 in the wafer heating apparatus 1 according to the secondembodiment. This is a preferable example wherein, among the threering-shaped resistive heating member zones shown in FIG. 7A, theresistive heating member zone 4 eh located outside is divided into fourequal fan-shaped resistive heating member zones 4 e, 4 f, 4 g, 4 h, andthe resistive heating member zone 4 cd located inside is divided in thecircumferential direction into two equal fan-shaped resistive heatingmember zones 4 c, 4 d. Specifically, among the three ring-shapedresistive heating member zones 4 b, 4 cd and 4 eh, the innermostring-shaped resistive heating member zone 4 b is the ring-shapedresistive heating member zone 4 b consisting of a ring, while theresistive heating member zone 4 cd located outside thereof is dividedinto two equal parts of fan-shaped resistive heating member zones 4 c, 4d, and the resistive heating member zone 4 eh located outside thereof isdivided in the circumferential direction into four equal parts offan-shaped resistive heating member zones 4 e, 4 f, 4 g and 4 h. Such aconfiguration is preferable as it achieves uniform temperaturedistribution over the surface of the wafer W, by dividing the ringlocated at the outer position into larger number of parts.

The resistive heating member zones 4 a through 4 g of the wafer heatingapparatus 1 shown in FIG. 7B are provided with the resistive heatingmembers 5 a through 5 g that can independently control the heatgeneration, respectively.

However, the zone 4 a and the zone 4 b may be connected with each otherin parallel or series so as to be controlled as a single circuit, if theoutside environment of the wafer heating apparatus 1 would not bechanged frequently. With this constitution, a through hole for insertingthe lift pin that lifts the wafer W can be provided between the zone 4 aand the zone 4 b.

While the ring-shaped resistive heating member zone 4 cd is divided intotwo parts each having center angle of 180 degrees and the ring-shapedresistive heating member zone 4 eh is divided into four parts eachhaving center angle of 90 degrees in the second embodiment, the presentinvention is not limited to this constitution and the zone may bedivided into three or more parts.

In FIG. 7B, the resistive heating member zones 4 c, 4 d are divided by astraight border line, but it needs not necessarily be a straight lineand may be a wavy line. The resistive heating member zones 4 c, 4 d arepreferably symmetrical with respect to the center of the resistiveheating member zone.

Similarly, border lines between the resistive heating member zones 4 eand 4 f, 4 f and 4 g, 4 g and 4 h and 4 h and 4 e need not necessarilybe straight lines but may be wavy lines. These zones are also preferablysymmetrical with respect to the center of the resistive heating memberzone.

According to the present invention, it is preferable to form theresistive heating members 5 by printing method or the like, and theresistive heating members 5 have dimensions of 1 to 5 mm in width and 5to 50 μm in thickness. When a large area is printed at a time, there mayarise unevenness in thickness of the printed layer due to difference inpressure between a squeegee and a screen across the printed surface.Especially when the resistive heating member 5 is large in size,thickness of the resistive heating member 5 becomes uneven across thesurface, resulting in varying amount of heat generated. Varying amountof heat generated leads to larger temperature difference across thesurface of the wafer W. In order to prevent difference in temperaturefrom occurring due to the varying thickness of the resistive heatingmember, it is effective to divide the resistive heating member 5 oflarge diameter.

In the example of the second embodiment shown in FIG. 7A, the area ofthe resistive heating member 5 to be printed in the resistive heatingmember zone 4 can be made smaller since the ring-shaped resistiveheating member zone 4 cd of the concentric rings except for the centralportion of the wafer W mounting surface 3 is divided into two parts, andthe ring-shaped resistive heating member zone 4 eh of the larger ring isdivided into four parts. As a result, thickness of the resistive heatingmember 5 can be made uniform. Moreover, slight difference in temperatureacross the surface of the wafer W can be corrected and uniformtemperature distribution over the surface of the wafer W can beachieved. In order to make fine adjustment of resistance of the band ofthe resistive heating member 5, a long groove may be formed along theresistive heating member by means of laser or the like, therebyadjusting the resistance.

The resistive heating members 5 a, 5 b, 5 c, 5 d, 5 e, 5 f, 5 g, 5 hshown in FIG. 6 each consists of the first arced sections 51 and thelinkage section 52 which is a turn-back band. The linkage section 52preferably has arc shape rather than straight, since arc shape enablesit to minimize the temperature difference across the surface of wafer.

In the wafer heating apparatus 1 according to the present invention, itis preferable that distance S3 between the resistive heating member zone4 cd and the outermost ring-shaped resistive heating member zone 4 eh islarger than the distance S2 between the resistive heating member zone 4b and the resistive heating member zone 4 cd as shown in FIG. 7A. Whenthe distance S3 of the outside is larger than the distance S2 of theinside in a constitution where two or three ring-shaped resistiveheating member zones 4 are provided, the large width S3 of thering-shaped resistive heating member zone 4 where the resistive heatingmember 5 is not formed enables it to expose a larger portion of thesurface of the plate-shaped member 2 which is not covered by theresistive heating member 5, thereby increasing the effect of cooling. Italso increases the heat conductivity of the plate-shaped member 2 viathe insulation layer that constitutes the exposed portion, thusresulting in higher efficiency of cooling and faster rate of cooling theheater section 7.

It is preferable that a plurality of the nozzles 24 are provided in sucha manner that the tips 24 a thereof are projected onto the area betweenthe outermost ring-shaped resistive heating member zone 4 eh and theresistive heating member zone 4 cd located inside thereof in the othersurface of the plate-shaped member 2. While the ring-shaped regionhaving width S3 is devoid of the resistive heating member where theplate-shaped member 2 having high heat conductivity is covered by theinsulation layer 14 and the insulation layer 12, there occurs large heattransfer from the surface to the plate-shaped member 2 and the coolinggas discharged from the top 24 a of the nozzle 24 directly hits thisportion so that heat can be removed quickly from the plate-shaped member2, thereby to cool down the heater section 7 in a short time. It ispreferable that a plurality of the cooling nozzles 24 are provided alongthe region of width S3. For example, in the case of processing a wafermeasuring 200 to 300 mm in diameter, the number of nozzles 24 ispreferably 4 to 16 which enables it to effectively cool down the heatersection 7. While the cooling nozzles 24 are provided along the region ofwidth S3 in the example described above, it is preferable to provide aplurality of nozzles 24 in the mid portion along a circle since it isdifficult to decrease the temperature of the mid portion with thenozzles provided only in the region of width S3.

In the wafer heating apparatus 1 of the present invention, it ispreferable to make the surfaces of the insulation layers 12, 14 and/orthe resistive heating member 5 unsmooth. When the surface of theinsulation layer 14 which opposes the tip of the nozzle 24 shown in FIG.8 and FIG. 9 and the surface of the insulation layer 12 a shown in FIG.10 have protrusions and recesses, the cooling gas discharged from thenozzle 24 hits the surface having protrusions and recesses of theinsulation layers 12, 14 and the heat of the plate-shaped member 2 istransferred efficiently via the insulation layers 12, 14 to the coolinggas. In other words, this constitution is preferable since it makes heatexchange with the cooling gas easier to undergo on the surface havingprotrusions and recesses, thus increasing the effect of cooling theheater section 7. When the surface of the resistive heating member 5shown in FIG. 8 has protrusions and recesses, a part of the cooling gasthat has hit the insulation layer 14 flows along the insulation surface14 and passes the surface of the resistive heating member 5 whilecarrying out heat exchange with higher efficiency with the surface ofthe resistive heating member 5, thus resulting in improved effect ofremoving heat from the heater section 7 via the resistive heatingmember. It is more preferable that the resistive heating member 5 andthe insulation layer 14 have surface having protrusions and recesses.

When the surfaces of the insulation layers 12, 14 and the resistiveheating member 5 have protrusions and recesses, should microscopiccracks occur in the insulation layers 12, 14 and the resistive heatingmember 5 due to thermal stress generated by the difference in thermalexpansion between the insulation layers 12, 14 and the resistive heatingmember 5 and the plate-shaped member 2, the protrusions and recesses ofthe surface mitigate the stress at the tips of the cracks, so as toprevent the cracks from developing.

The surface having protrusions and recesses preferably has substantiallylattice-like configuration. FIG. 11 shows an example where theinsulation layer 12 has surface having protrusions and recesses. Whenthe nozzles 24 are provided in such a manner that the tips 24 a thereofare projected onto the surface having protrusions and recesses 401between the resistive heating member 5 in the other surface of theplate-shaped member 2, the cooling gas hits the surface havingprotrusions and recesses 401 so that heat exchange between the coolinggas and the surface having protrusions and recesses 401 becomes easierthus resulting in improved effect of cooling by removing heat from theheater section 7 via the surface having protrusions and recesses 401.When surface having protrusions and recesses 401 has substantiallylattice-like configuration, the cooling gas that has hit the recess 42then hits the side face of the protrusion 41 so as to carry out heatexchange, and the cooling gas can flow over a longer distance throughthe groove formed along a straight line, thus making it easier to carryout heat exchange through the surface having protrusions and recesses401. When the surface having protrusions and recesses 401 hassubstantially lattice-like configuration, heat exchange between thecooling gas and the surface having protrusions and recesses 401 isincreased thereby making it easier to cool down the heater section 7 ina shorter period of time.

The number of the grooves of the lattice configuration is preferablyfrom 0.2 to 80, more preferably from 0.4 to 40 per 1 mm of width. Whenthe number of the grooves is less than 0.2 per 1 mm, the effect ofcooling through heat exchange decreases and such troubles as peel-off ofthe resistive heating member 5 and the insulation layers 12, 14 or crackmay occur when the resistive heating member 4 is subjected to repetitivecycles of heating and cooling.

When the number of the grooves is more than 80 per 1 mm, flow of thecooling gas into the recess 42 may be hampered, thus resulting in lowerefficiency of cooling. It also makes the grooves too small, which givesrise to the possibility of cracks occurring in the recess 42 andextending to the insulation layers 12, 14 and the resistive heatingmember 5. By controlling the number of the grooves in the surface havingprotrusions and recesses 401 within the range from 0.4 to 80 per 1 mm,it is made easier to carry out heat exchange between the heater section7 and the cooling gas. Thus it is made possible to provide the waferheating apparatus 1 of high reliability where the difference in thermalexpansion between the insulation layers 12, 14 and the resistive heatingmember and the plate-shaped member 2 is absorbed and deterioration ofthe resistive heating member 5 can be suppressed.

While the common wisdom may dictate that deterioration of the resistiveheating member 5 can be, suppressed by making the insulation layer 12thicker, the insulation layer 12 serving as the protective layer isformed from a material different from that of the resistive heatingmember 5, and therefore the difference in thermal expansion between thematerials cancels the effect of mitigating the stress. In other words,excessive thickness of the insulation layer 12 may generate asignificant stress in the insulation layer 12 when it is baked, thusresulting in lower reliability. Accordingly, the present invention hasbeen completed on the basis of finding that it is effective inpreventing deterioration of the resistive heating member 5 withoutincreasing the overall thickness of the insulation layer 12, to make thesurfaces of the insulation layers 12, 14 and/or the resistive heatingmember 5 of the plate-shaped member 2 unsmooth, preferably insubstantially lattice configuration.

By forming the insulation layer 12 which covers the resistive heatingmember 5 in substantially lattice configuration, it is made possible tohold the resistive heating member 5 firmly with the protrusion of thesubstantially lattice configuration of the insulation layer, 12, so thatthe resistive heating member 5 does not peel off.

Since the overall thickness of the insulation layer 12 is not large, andthe stress due to the difference in thermal expansion is mitigated inthe recess 42 of the substantially lattice configuration, troubles suchas crack do not occur. This applies also to the plate-shaped member 2,the insulation layer 14 and the resistive heating member 5, and it canbe seen that it is better to form the resistive heating member 5 insubstantially lattice configuration.

The surface having protrusions and recesses 401 preferably has suchcharacteristics as the proportion (tp/tv)×100 of the thickness (tp) ofthe protrusion 41 to the thickness (tv) of the recess 42 is in a rangefrom 102 to 200%, and mean thickness of the resistive heating member 5or the insulation layers 12, 14 is in a range from 3 to 60 μm. Thisconstitution makes it possible to provide the wafer heating apparatus 1of extremely high reliability where the difference in thermal expansionbetween the resistive heating member and the plate-shaped member 2 isabsorbed and deterioration of the resistive heating member 5 can besuppressed.

When the proportion (tp/tv)×100 is less than 102, efficiency of heatexchange becomes lower and the tolerable cycles of heating and coolingbefore crack occurs becomes less than 4200, which is not desirable.

When the proportion exceeds 200%, the difference between the protrusion41 and the recess 42 becomes too large and leads to a large temperaturedifference, and the tolerable cycles of heating and cooling before crackoccurs may decrease.

When mean thickness of the insulation layers 12, 14 is less than 3 μm,variation in thickness of the resistive heating member 5 formed byprinting method becomes 30% or larger, and the temperature differenceacross the surface of the wafer W may becomes large.

When mean thickness of the insulation layers 12, 14 is more than 60 μm,microscopic cracks may occur in the insulation layers 12, 14 due to thedifference in thermal expansion between the insulation layers 12, 14 andthe plate-shaped member 2.

Thickness (tv) of the recess may be given in terms of mean value of 5positions around the center of each recess 42. Thickness (tp) of theprotrusion may be given in terms of mean value of maximum thickness at 5positions of each protrusion 41. The mean thickness may be given byaveraging the thickness of the recess 42 and the thickness of theprotrusion 41.

FIG. 9B is a plan view showing an example of the wafer heating apparatus1 of the present invention where the insulation layer 12 is formed.Among the three ring-shaped resistive heating member zones 4 b, 4 cd and4 eh, the insulation layer 12 eh that covers the resistive heatingmember zone 4 eh located outside is preferably ring-shaped. It ispreferable that the three ring-shaped insulation layers 12 b, 12 cd, 12eh individually cover the resistive heating member zones 4 b, 4 cd and 4eh, respectively, which equalize the surface temperature of the wafer W,and the insulation layer 12 is formed in accordance.

In the wafer heating apparatus 1 of the present invention, it ispreferable that the distance S6 is larger than the other distances S4and S5 as shown in FIG. 9B. The distance S4 is the distance between theinsulation layer 12 a of circular shape located at the center and theconcentric ring-shaped insulation layer 12 b located outside thereof.The distance S5 is the distance between the insulation layer 12 b ofring shape and the ring-shaped insulation layer 12 cd located outsidethereof. The distance 56 is the distance between the insulation layer 12cd of ring shape and the outermost ring-shaped insulation layer 12 eh.

When the distance S6 is larger than S4 and S5, a larger portion of thesurface of the plate-shaped member 2 can be exposed since ring-shapedregion having width of 56 devoid of the insulation layer 12 becomeslarger, thereby increasing the effect of cooling. It also leads to moreheat transfer through the insulation layers 12, 14 that constitute theexposed portion, thus resulting in improved cooling efficiency throughhigh heat conductivity of the plate-shaped member 2 and faster rate ofcooling the heater section 7.

In case the plate-shaped member 2 is made of sintered silicon carbide orsintered aluminum nitride, the plate-shaped member 2 may be heated at atemperature from 800 to 1200° C. so as to form an insulating oxide filmon the surface of the plate-shaped member 2, and use the oxide film asthe insulation layer 14.

The resistive heating member zone and the resistive heating member inthe wafer heating apparatus 1 of the second embodiment will now bedescribed in detail.

In order to minimize the temperature difference across the surface ofthe wafer W in the wafer heating apparatus 1 of the second embodiment,it is preferable to set the outer diameter D1 of the resistive heatingmember zone 4 a located at the center in a range from 20 to 40% of theouter diameter D of the ring-shaped resistive heating member zone 4 ehlocated along the periphery, outer diameter D2 of the resistive heatingmember zone 4 b located outside thereof in a range from 40 to 55% of theouter diameter D of the resistive heating member zone 4 eh located alongthe periphery, and set the outer diameter D3 of the ring-shapedresistive heating member zone 4 cd located outside of the resistiveheating member zone 4 b in a range from 55 to 85% of the outer diameterD of the ring-shaped resistive heating member zone 4 eh located at theoutermost position.

The outer diameter D of the resistive heating member zone 4 eh locatedalong the periphery is the diameter of the circle that circumscribes tothe resistive heating, member 5 eh located at the outermost position inthe resistive heating member zone 4 eh. The outer diameter D2 of theresistive heating member zone 4 b is the diameter of the circle thatcircumscribes to the resistive heating member 5 b located at theoutermost position in the resistive heating member zone 4 b. The outerdiameter D3 is the diameter of the circle that circumscribes to theresistive heating member Scd. Definition of the circumscribed circle ismade by using the arc section excluding the protruding portions of theresistive heating member connected to the power feeder section.

The outer diameters are preferably in the ranges described above for thefollowing reasons.

When the outer diameter D1 is less than 20% of D, temperature of the midportion of the resistive heating member zone 4 a would not risesufficiently even if the resistive heating member zone 4 a is caused togenerate more heat, due to the small outer diameter of the centralresistive heating member zone 4 a. When the outer diameter D1 is morethan 40% of D, temperature of the resistive heating member zone 4 awould become too high along the periphery thereof when the temperatureof the mid portion of the resistive heating member zone 4 a is raised,due to the large outer diameter of the resistive heating member zone 4 alocated at the center. The outer diameter D1 is preferably in a rangefrom 20% to 30%, and more preferably from 23 to 27% of D, which makes itpossible to further decrease the temperature difference across thesurface of the wafer W.

When the outer diameter D2 is less than 40% of the outer diameter D,since the wafer heating apparatus 1 tends to cool down along theperiphery, an attempt to prevent temperature of the wafer W along theperiphery thereof from decreasing by causing the resistive heatingmember zone 4 cd to generate more heat would result in highertemperature of the resistive heating member zone 4 cd in an innerportion thereof nearer to the center of the wafer W, thus increasing thetemperature difference across the wafer surface. When the outer diameterD2 is more than 55% of the outer diameter D, an attempt to prevent thetemperature of the wafer W along the periphery thereof from decreasingby causing the resistive heating member zone 4 cd to generate more heatraises the temperature of the resistive heating member zone 4 cdalthough the effect of decreasing temperature of the wafer W along theperiphery thereof reaches the ring-shaped resistive heating member zone4 b, thus resulting in lower temperature of the resistive heating memberzone 4 b along the periphery thereof. The outer diameter D2 ispreferably in a range from 41% to 53%, and more preferably from 43 to49% of the outer diameter D, which makes it possible to further decreasethe temperature difference across the wafer surface.

When the outer diameter D3 is less than 55% of the outer diameter D,since the wafer heating apparatus 1 tends to cool down along theperiphery thereof, an attempt to prevent the temperature of the wafer Walong the periphery thereof from decreasing by increasing the heatgeneration from the resistive heating member zone 4 eh would result inhigher temperature of the resistive heating member zone 4 eh in theinner portion thereof nearer to the center of the wafer W, thusincreasing the temperature difference across the surface of the wafer W.When the outer diameter D3 is more than 85% of the outer diameter D, anattempt to prevent the temperature of the wafer W along the peripherythereof from decreasing by causing the resistive heating member zone 4eh to generate more heat raises the temperature of the resistive heatingmember zone 4 eh, although the effect of decreasing temperature of thewafer W along the periphery thereof reaches the resistive heating memberzone 4 cd, thus resulting in lower temperature of the resistive heatingmember zone 4 cd along the periphery thereof. The outer diameter D3 ispreferably in a range from 65% to 85%, and more preferably from 67 to70% of the outer diameter D, which makes it possible to further decreasethe temperature difference across the surface of the wafer W.

Dimensions of the resistive heating member zone 4 have been described indetail so far. The resistive heating member zone 4 of the presentinvention is characterized mainly by the fact that annular no-heaterzone can be provided in that the resistive heating member 5 does notexist between the ring-shaped regions. Existence of the no-heater zonemakes it possible to form the support pin 15, the through hole 26 andthe powder feeder section 6 in the no-heater zone. Thus it is madeeasier to prevent temperature difference from being caused by thesupport pin 15, the through hole 26 and the powder feeder section 6,thus making the temperature difference across the surface of wafer lesslikely to increase.

The diameter D11 of a central portion of the resistive heating memberzone 4 a where the resistive heating member is not formed may be set inrange from 5 to 10% of the diameter D. This allows it to provide thesupport pins 15, for example, within the circle of diameter D11, so asto prevent the temperature of the wafer surface from decreasing due tothe support pins 15.

It is preferable that inner diameter D22 of the resistive heating memberzone 4 b is in a range from 34 to 45% of the outer diameter D. Settingin this range allows it to provide a ring-shaped no-heater zone of asize about 1 to 22% of diameter between rings 4 a and 4 b, thus makingpossible to minimize the decrease in temperature of the wafer surfaceeven when the lift pin 25, etc. is provided in this region. Innerdiameter D22 is preferably from 36 to 41% of the diameter D. Setting inthis range allows it to provide through hole which penetrates theplate-shaped member between the first resistive heating member and thesecond resistive heating member.

Inner diameter D33 of the resistive heating member zone 4 cd ispreferably set in a range from 50 to 65% of the diameter D, which allowsit to provide a ring-shaped no-heater zone where the resistive heatingmember does not exist between the resistive heating member zone 4 b andthe resistive heating member zone 4 cd. Since this constitution makes itpossible to provide the powder feeder section 6 for supplying electricalpower to the resistive heating members in the ring-shaped no-heaterzone, cold spot or the like can be prevented from being generated in thesurface of the wafer W due to the power feeder section 6. Inner diameterD33 is more preferably in a range from 58 to 63% of the diameter D.

The inner diameter D0 of the resistive heating member zone 4 eh can beset in a range from 85 to 93% of the diameter D. This makes it possibleto provide a ring-shaped no-heater zone between the resistive heatingmember zone 4 eh and the resistive heating member zone 4 cd. Thus it ismade easy to heat the wafer W without increasing the temperaturedifference across the wafer surface, by providing the support pins 15that support the object to be heated such as wafer W, and the powerfeeder section 6 in the annular no-heater zone. Inner diameter D0 ismore preferably in a range from 90 to 92% of the diameter D.

In the other principal surface of the plate-shaped member 2, diameter Dof the circumscribed circle C of the resistive heating member 5 locatedat the outermost position is preferably in a range from 90 to 97% of thediameter DP of the plate-shaped ceramic member 2.

When diameter D of the circumscribed circle C of the resistive heatingmember 5 is smaller than 90% of the diameter DP of the plate-shapedceramic member 2, it takes longer time to raise or lower the temperatureand therefore results in unfavorable temperature characteristic of thewafer W when the wafer is quickly heated or cooled down. For the purposeof achieving uniform temperature distribution over the surface of thewafer W so that temperature of the wafer W does not become lower alongthe periphery, diameter D is preferably about 1.02 times the diameter ofthe wafer W. When the diameter DP of the plate-shaped ceramic member 2is larger than the range described above in relation to the size of thewafer W, size of the wafer W becomes too small in relation to thediameter DP of the plate-shaped ceramic member 2, and the efficiency ofheating the wafer W for the input power becomes lower. Moreover, largersize of the plate-shaped ceramic member 2 results in larger installationarea of the wafer manufacturing apparatus, which is not desirablebecause it decreases the rate of operation of the semiconductormanufacturing apparatus.

When diameter D of the circumscribed circle C of the resistive heatingmember S is larger than 97% of the diameter DP of the plate-shapedceramic member 2, the space between the contact member 18 and theperiphery of the resistive heating member 5 becomes too small and heatdissipates unevenly from the resistive heating member 5 into the contactmember 18. Particularly, since heat is transferred through the contactmember 18 also from the portion along the periphery near thecircumscribed circle C where the arc band 51 does not exist (forexample, the portion indicated by P in FIG. 6), temperature may becomelower in the portion P, thus resulting in larger temperature differenceacross the wafer surface. According to the present invention, diameter Dof the circumscribed circle C of the resistive heating member 5 is setpreferably in a range from 92 to 95% of the diameter DP of theplate-shaped ceramic member 2.

In the wafer heating apparatus 1 of the present invention, it ispreferable that distance L1 (width of the no-heater zone P) between theoutermost arc bands 51 that make contact with the circumscribed circle Cof the resistive heating member 5 shown in FIG. 6 is smaller than thedifference between the diameter DP of the plate-shaped ceramic member 2and the diameter D of the circumscribed circle C (hereinafter referredto as LL). When the distance L1 is larger than LL, there is apossibility that heat of the no-heater zone P is transferred to theperipheral portion of the plate-shaped ceramic member, therebydecreasing the temperature of the no-heater zone P. When the distance L1is smaller than LL, temperature of the no-heater zone P is less likelyto decrease and the temperature difference across the surface of waferdecreases without lowering the temperature of the peripheral portion ofthe wafer W mounted on the mounting surface 3 of the plate-shapedceramic member 2.

In order to prevent the temperature of the no-heater zone P fromlowering, it is necessary to raise the temperature of the no-heater zoneP. When the resistance of the linkage arc band 52 that heats theno-heater zone is set to a similar level or slightly higher so as toincrease the amount of heat generation, it is made possible to achieveuniform temperature distribution over the surface of the wafer W. Whenthe resistive heating member 5 is formed by printing process or thelike, the resistance of the small arc band 52 can be made higher bymaking the width Ws of the linkage arc band 52 smaller by 1 to 5% thanthe width Wp of the arc band 51, thereby making the temperature of thesmall arc band 52 higher than the temperature of the arc band 51,thereby achieving uniform temperature distribution across the surface ofthe wafer W.

In the wafer heating apparatus 1 wherein one of the principal surfacesof the plate-like ceramic member 2 having thickness from 1 to 7 mm isused as the mounting surface 3 to place the wafer W thereon and theresistive heating member 5 is formed on the bottom surface of theplate-shaped ceramic member 2, it is preferable that thickness of theresistive heating member 5 is in a range from 5 to 50 μm and the areaoccupied by the resistive heating member 5 within the circumscribedcircle C is in a range from 5 to 30% of the area of the circumscribedcircle C that surrounds the resistive heating member 5 on the othersurface of the plate-like ceramic member 2.

When the area occupied by the resistive heating member 5 in thecircumscribed circle C is less than 5% of the area of the circumscribedcircle C that surrounds the resistive heating member 5, distances L1, L2etc. between the adjacent resistive heating members 5 become too large,and therefore temperature of a portion of the mounting surface 3corresponding to the distance L1 that does not include the resistiveheating member 5 becomes lower than that of the other portions, thusmaking it difficult to achieve uniform temperature distribution of themounting surface 3.

When the area occupied by the resistive heating member 5 in thecircumscribed circle C is larger than 30% of the area of thecircumscribed circle C that surrounds the resistive heating member 5, onthe other hand, thermal stress due to difference in the thermalexpansion coefficient becomes large enough to deform the plate-shapedceramic member 2, even when the difference in the thermal expansioncoefficient between the plate-shaped ceramic member 2 and the resistiveheating member 5 is controlled within 2.0×10⁻⁶/° C. Even when theplate-shaped ceramic member 2 is made of a sintered ceramic materialthat is hard to deform, thickness t of the plate-shaped ceramic member 2is as small as 1 to 7 mm, and therefore the plate-shaped ceramic member2 may warp to become concave on the mounting surface 3 when theresistive heating member 5 is energized to heat. As a result, differencein temperature may become large, with the temperature of the wafer Wbecoming higher around the center than along the periphery.

The area occupied by the resistive heating member 5 in the circumscribedcircle C is more preferably in a range from 7 to 20%, and furthermorepreferably from 8% to 15% of the area of the circumscribed circle C thatencloses the resistive heating member 5.

While there is a region where the linkage bands 52 oppose each otherbetween different resistive heating members 5 or in a same resistiveheating member, distance L1 between the linkage bands 52 in the regionis preferably 0.5 mm or more and not more than three times the thicknessof the plate-shaped ceramic member 2. When distance L1 is less than 0.5mm, whisker-like protrusion that can cause short-circuiting may beproduced in the region in which the resistive heating members 5 opposeeach other, when printing the resistive heating member 5. When distanceL1 is more than three times the thickness of the plate-shaped ceramicmember 2, a cold zone may be produced on the surface of the wafer W atposition near the region corresponding to the distance L1, thusincreasing the temperature difference across the surface of the wafer W.In order to prevent the opposing resistive heating members in the regionfrom short-circuiting and efficiently achieve the effect describedabove, thickness of the resistive heating member 5 is preferably in arange from 5 to 50 μm.

When thickness of the resistive heating member 5 is less than 5 μm, itbecomes difficult to form the resistive heating member 5 with uniformthickness by the screen printing process. When thickness of theresistive heating member 5 is larger than 50 μm, the resistive heatingmember 5 becomes too rigid due to the relatively large thickness, evenwhen the area occupied by the resistive heating member 5 is set to notlarger than 30% of the area of the circumscribed circle C. As a result,the plate-shaped ceramic member 2 may be deformed due to expansion andshrinkage of the resistive heating member 5 caused by the temperaturechange of the plate-shaped ceramic member 2. Also it becomes difficultto form the resistive heating member 5 with uniform thickness by thescreen printing process, resulting in large temperature differenceacross the surface of the wafer W. Thickness of the resistive heatingmember 5 is more preferably in a range from 10 to 30 μm.

Temperature of the heater section 7 is preferably measured by means of aplurality of temperature sensors 10 of which distal ends are embedded inthe plate-shaped ceramic member 2 in correspondence to the resistiveheating members 5 which can be heated independently. For the temperaturesensors 10, it is preferable to use thermocouples of sheathed typehaving outer diameter of 0.8 mm or less, in consideration of theresponse characteristic and the ease of maintenance. However,thermocouple of bare wire type having outer diameter of 0.5 mm or lessor a thermistor such RTD may also be used. The distal ends of thetemperature sensors 10 are preferably secured in holes formed in theplate-shaped ceramic member 2 while being pressed against the inner wallsurface of the hole by means of a fastening member provided in the hole,in order to ensure the reliability of measurement.

Heat conductivity of the plate-shaped member 2 is preferably higher thanthat of the insulation layer 14. When heat conductivity of theplate-shaped ceramic member 2 is high, heat is transferred from theinside of the plate-shaped ceramic member 2 resulting in faster rate ofcooling the heater section 7, when the plate-shaped ceramic member 2 iscooled by the cooling gas applied thereto. The insulation layer 12 andthe insulation layer 14 are preferably formed from glass or insulatingresin having heat conductivity of 1 to 10 W/(m·K). The plate-shapedmember 2 is preferably made of ceramics such as carbide or nitride thathas heat conductivity of 50 to 280 W/(m·K).

It becomes difficult to manufacture when the difference in thermalexpansion coefficient between the resistive heating member 5 and theplate-shaped member 2 is 0.1×10⁻⁶/° C. or less. When the difference inthermal expansion coefficient between the resistive heating member 5 andthe plate-shaped member 2 is more than 3.0×10⁻⁶/° C. or, the resistiveheating member 5 may warp in concave shape on the side of the mountingsurface 3 due to the thermal stress acting between the resistive heatingmember 5 and the plate-shaped member 2 when the resistive heating member5 is heated.

The glass used to form the insulation layer 12 may be either crystallineor amorphous in nature, a material having durable temperature of 200° C.or higher and difference in thermal expansion coefficient from that ofthe ceramics forming the plate-shaped ceramic member 2 is in a range of±1×10⁻⁶/° C. and more preferably from −5×10⁻⁷/° C. to +5×10⁻⁷/° C. in atemperature range from 0 to 200° C. is preferably used. Use of glasshaving a value of thermal expansion coefficient out of the rangedescribed above may lead to defects such as crack and peel-off whencooled down after bonding the glass due to large difference from thethermal expansion coefficient of the ceramics that forms theplate-shaped member 2.

It is preferable that the glass that forms the insulation layer 12 isamorphous glass which consists mainly from SiO₂ and includes 10% byweight on oxide basis or more of at least one kind selected from amongB, Mg, Ca, Pb and Bi, and does not substantially include oxide of As orSb (0.05% by weight or less on oxide basis).

Viscosity at a high temperature can be made lower with the glass havingthe composition described above. Inclusion of B, Mg, Ca, Pb or Bi isaimed at decreasing the apparent viscosity of the glass throughdispersion of SiO₂ glass. PbO, B₂O₃ and Bi₂O₃ do not crystallize andremain in the glass so as to lower apparent viscosity and melting pointof the glass, and are therefore effective in suppressing the generationof bubbles in the glass.

By lowering the viscosity of the glass, it is made possible to cause thebubbles generated in the insulation layer 12 to float to the surface ofthe insulation layer 12 so as to become open pores, thereby decreasingbubbles remaining in the insulation layer 12. Thus such a glass layercan be formed as a region free from bubbles continues over 10 μm or morein the direction of thickness of the insulation layer 12. Use ofamorphous glass is preferable since it makes it easier to form theinsulation layer 12 including less bubbles than crystallized glass. Thusit is made possible to decrease bubbles in the insulation layer 12without adding oxide of toxic As or Sb that has the effect of removingbubbles.

When the content of B, Mg, Ca, Pb and/or Bi is less than 10% by weighton oxide basis, viscosity of the glass at a high temperature cannot bemade sufficiently low, and it becomes difficult to decrease bubbles.When crystallized glass is used, the glass expands or shrinks during theprocess of nucleation. During the expansion and shrinkage, a largenumber of minute bubbles are generated around the crystal nuclei whichdecrease the withstanding voltage of the insulation layer. Therefore, itis not preferable to use crystallized glass as it makes it difficult toprevent the occurrence of defects in the glass that constitutes theinsulation layer 12, in comparison to the case of using amorphous glass.

The glass that constitutes the insulation layer 12 preferably includesalkali content in concentration not higher than 2% by weight. Whilealkali content added to the glass is effective in decreasing theviscosity, it leads to a problem related to the durability throughmigration of the glass component. When alkali content in the glass thatconstitutes the insulation layer 12 is controlled to within 2% byweight, durability is improved as determined in durability test in whichthe resistive heating member 5 is heated by applying a DC voltage to theresistive heating member 5. It was found that durable life in continuousdurability test conducted at 250° C. can be extended to 1000 hours whenalkali content in the glass that constitutes the insulation layer 12 isnot higher than 2% by weight, and 5000 hours when alkali content is nothigher than 1% by weight. The alkali content refers to oxides of alkalimetals such as Li₂O, Na₂O and K₂O.

The glass of the insulation layer 12 is preferably formed by applying apaste prepared by blending a plurality of glass powders each having meanparticle size D50 of 15 μm or less and differing in mean particle sizeD50 by 20% or more from each other, and controlling the process ofremoving the binder so that remaining carbon content is 1% by weight orless with respect to the weight of glass.

By blending a plurality of glass powders having different mean particlesizes, it is made possible to increase the density of the packed glasspowder and thereby decrease the bubbles in the insulation layer. Bycontrolling the process of removing the binder so that remaining carboncontent is 1% by weight or less with respect to the weight of glass, itis made possible to suppress the reaction between the carbon included inthe binder and the oxygen included in the glass and increase the bulkdensity of the glass powder after the process of removing the binder, sothat such a glass layer can be formed more easily as a region free frombubbles continues over 10 μm or more in the direction of thickness ofthe insulation layer.

In case a plurality of glass powders each having mean particle size D50larger than 15 μm or differing in mean particle size D50 by less than20% from each other are used in the process of forming the insulationlayer 12, the glass cannot be packed densely enough and it is difficultto fill in the voids between the glass particles. Also in case carboncontent of more than 1% by weight or less with respect to the weight ofglass remains in the process of removing the binder, it is difficult tosuppress the generation of bubbles.

Baking temperature of the glass is preferably not lower than the workingtemperature (104 poise or less in terms of viscosity of the glass).

Third Embodiment

The wafer heating apparatus according to the third embodiment of thepresent invention will now be described.

FIG. 13 is a sectional view showing the constitution of the waferheating apparatus 1 according to the third embodiment, comprising theplate-shaped member 2 having one of the principal surfaces thereofserving as the mounting surface 3 to mount a wafer W thereon and theother principal surface having the band-shaped resistive heating member5 of one or more circuits formed thereon, with an insulation layer 60formed thereon as required. The power feeder section 6 is provided tosupply electric power to the resistive heating members 5 independentlyfrom each other, and the casing 19 is provided to enclose the powerfeeder section 6.

The lift pin not shown is provided so as to be capable of movingvertically and load the wafer W onto the mounting surface 3 or unload ittherefrom.

The cooling nozzle 24 that discharges the cooling gas is provided on thebottom surface 21 of the casing 19.

The cooling gas discharged from the cooling nozzle 24 is blown onto theunder surface of the plate-shaped member 2 so as to remove heat from theunder surface of the plate-shaped member 2. The cooling gas that hasbeen heated is purged to the outside through the hole formed in thebottom 21 of the metal casing 19 while transferring the heat to thecasing 19, thereby quickly cooling down the plate-shaped member 2.

To heat the wafer W with the wafer heating apparatus 1, the wafer W thathas been transferred to above the mounting surface 3 by a transfer arm(not shown) is held by the lift pins (not shown), then the lift pins arelowered thereby to place the wafer W on the mounting surface 3.

Then electric power is supplied through the power feeder section 6 so asto heat the resistive heating member 5 and heat the wafer W placed onthe mounting surface 3 via the plate-shaped member 2.

The wafer heating apparatus 1 of the third embodiment is characterizedin that the surface of the resistive heating member 5 is surface havingprotrusions and recesses 55.

FIG. 14A is a perspective view showing the surface having protrusionsand recesses 55, and FIG. 14B is a sectional view thereof.

In the wafer heating apparatus 1 of the third embodiment, the resistiveheating member 5 is prevented from breaking by forming the surface ofthe resistive heating member 5 as the surface having protrusions andrecesses 55. Specifically, temperature of the resistive heating member 5rises quickly when it is supplied with electric power. This quick riseof temperature generates thermal stress between the resistive heatingmember 5 and the plate-shaped ceramic member 2 due to the differences inthe temperature and in the thermal expansion coefficient between theresistive heating member 5 and the plate-shaped ceramic member 2. Thismay result in a significant compressive stress generated in theresistive heating member 5, which may break the resistive heating member5. It was found that this stress can be mitigated by forming the surfaceof the resistive heating member 5 as the surface having protrusions andrecesses 55.

That is, the significant compressive stress generated in the surface byheating and cooling can be distributed over a wide area of the surfacehaving protrusions and recesses 55, thereby preventing the peel-off andcrack of the resistive heating member 5 from occurring due to thestress. While repetition of heating and cooling of the resistive heatingmember 5 causes the stress to be generated repetitively in the resistiveheating member 5, it was found that tolerable thermal cycles of theresistive heating member 5 can be improved by mitigating the stress bymeans of the surface having protrusions and recesses 55.

While the surface having protrusions and recesses 55 of the resistiveheating member 5 has been described as an example, similar effect can beachieved also with the wafer heating apparatus having the insulationlayer 60 formed on the surface of the resistive heating member 5.

FIG. 15 is a perspective view showing an example of the wafer heatingapparatus according to a variation of the third embodiment, wherein theinsulation layer 60 is formed and the surface of the insulation layer 60is turned into surface having protrusions and recesses 61 in the waferheating apparatus shown in FIGS. 14A, 14B. By making the surface of theinsulation layer 60 as the surface having protrusions and recesses 61,peel-off and crack of the resistive heating member 5 can be preventedfrom occurring even when the resistive heating member 5 is subjected torepetitive cycles of heating and cooling. The surface of the resistiveheating member 5 under the insulation layer 60 may be either surfacehaving protrusions and recesses as shown in FIG. 15 or smooth surface.

The thermal stress generated due to the differences in the temperatureand in the thermal expansion coefficient tends to appear on the surfaceof the insulation layer 60 which faces the outside. When the surface isformed as the surface having protrusions and recesses 61, the stress canbe dispersed for a reason similar to that described in relation to theresistive heating member, so as to prevent the insulation layer 60 andthe resistive heating member 5 from peeling off or cracking.

It is preferable that the surface having protrusions and recesses 55, 61of the resistive heating member 5 and/or the insulation layer 60 of theplate-shaped member 2 are formed in substantially lattice configurationas shown in FIG. 14 and FIG. 15, which improves the effect of mitigatingthe stress. It is believed that lattice configuration makes it easierfor the stress to diffuse over the surface, thereby achieving the effectof mitigating the stress.

The number of the grooves of the lattice configuration is preferablyfrom 0.2 to 80, more preferably from 0.4 to 40 per 1 mm of width. Whenthe number of the grooves is less than 0.2 per 1 mm, the effect ofmitigating the stress decreases and so does the effect of preventingsuch troubles as peel-off of the resistive heating member 5 fromoccurring when the resistive heating member 5 is subjected to repetitivecycles of heating and cooling.

When the number of the grooves is more than 80 per 1 mm, it makes thegrooves too small, which gives rise to the possibility of cracksoccurring in the recesses 57, 63 and extending to the resistive heatingmember 5. By controlling the number of the grooves in the surface havingprotrusions and recesses 55 within the range from 0.4 to 80 per 1 mm, itis made possible to provide the wafer heating apparatus 1 of highreliability where the difference in thermal expansion between theplate-shaped member 2 and the resistive heating member 2 is absorbed anddeterioration of the resistive heating member 5 can be suppressed.

While the common wisdom may dictate that, deterioration of the resistiveheating member 5 can be suppressed by making the insulation layer 60thicker, the insulation layer 60 serving as the protective layer isformed from a material different from that of the resistive heatingmember 5, and therefore the difference in thermal expansion between thematerials cancels the effect of mitigating the stress. In other words,excessive thickness of the insulation layer 60 may generate asignificant stress in the insulation layer 60 when it is baked, thusresulting in lower reliability. Accordingly in the present invention, asthe means for preventing deterioration of the resistive heating member 5without increasing the overall thickness of the insulation layer 60, thesurfaces of the insulation layer 60 and/or the resistive heating member5 of the plate-shaped member 2 are turned into surface havingprotrusions and recesses, preferably in substantially latticeconfiguration.

By forming the insulation layer 60 which covers the resistive heatingmember 5 in substantially lattice configuration, it is made possible tohold the resistive heating member 5 firmly with the protrusion of thesubstantially lattice configuration of the insulation layer 60, so thatthe resistive heating member 5 does not peel off.

Since the overall thickness of the insulation layer 60 is not large, andthe stress due to the difference in thermal expansion is mitigated inthe recess 63 of the substantially lattice configuration, troubles suchas crack do not occur. This applies also to the plate-shaped member 2and the resistive heating member 5, and it can be seen that it is betterto form the resistive heating member 5 in substantially latticeconfiguration.

The surface having protrusions and recessess 55, 61 preferably has suchcharacteristics as the proportion (tp/tv)×100 of the thickness (tp) ofthe protrusion to the thickness (tv) of the recess is in a range from105 to 200%, and mean thickness of the resistive heating member 5 or theinsulation layer 60 is in a range from 3 to 60 μm. This constitutionmakes it possible to provide the wafer heating apparatus 1 of extremelyhigh reliability where the difference in thermal expansion between theresistive heating member 5 and the plate-shaped member 2 is absorbed anddeterioration of the resistive heating member 5 can be suppressed.

When the proportion (tp/tv)×100 is less than 105%, efficiency of heatexchange becomes lower and the tolerable number of cycles of heating andcooling before crack occurs becomes less than 4200, which is notdesirable.

When the proportion exceeds 200%, the difference between the protrusion56 and the recess 57 becomes too large and leads to a large temperaturedifference, and the tolerable number of cycles of heating and coolingbefore crack occurs may decrease.

When mean thickness of the insulation layer 60 is less than 3 μm,variation in thickness of the resistive heating member 5 formed byprinting method becomes 30% or larger, and the temperature differenceacross the surface of the wafer W may becomes large.

When mean thickness of the insulation layer 60 is more than 60 μm,microscopic cracks may occur in the insulation layer 60 due to thedifference in thermal expansion coefficient between the insulation layer60 and the plate-shaped member 2.

Thickness (tv) of the recess may be given in terms of mean value of 5positions around the center of the recesses 57, 63. Thickness (tp) ofthe protrusion may be given in terms of mean value of maximum thicknessat 5 positions of the protrusions 56, 62. The mean thickness may begiven by averaging the thickness of the recesses 57, 63 and thethickness of the protrusions 56, 62.

The resistive heating member 5 is preferably formed from a compositematerial consisting of at least two materials selected from among Pt, Auand Ag and glass. These metals are noble metals which have highresistance against oxidization and well match with the glass that holdsthe metals firmly.

The resistive heating member 5 is also preferably formed from Pt, Au andglass, or from Pt, Ag and glass, of which glass is more preferablyconstituted from the same components as those of the insulation layer60. This constitution improves the fusibility of the resistive heatingmember 5 and the insulation layer 60, and makes these members lesslikely to peel off each other and crack.

Composition of the composite material that constitutes the resistiveheating member 5 is preferably 20 to 40% by weight of Pt, 10 to 30% byweight of Au and 40 to 60% by weight of glass, and more preferably 30%of Pt, 20% of Au and 50% by weight of glass in case Pt and Au are used.

In case Pt and Ag are used, the composition is preferably 20 to 40% byweight of Pt, 10 to 30% by weight of Ag and 40 to 60% by weight ofglass, and more preferably 30% of Pt, 20% of Ag and 50% by weight ofglass

The glass is preferably crystallized glass having composition of ZnO,B₂O₃, SiO₂ and MnO₂, with ZnO being the main component. Preferablecomposition is 50 to 70% by weight of ZnO, 20 to 30% by weight of B₂O₃₁5 to 20% by weight of SiO₂ and 1 to 3% by weight of MnO₂.

The insulation layer 60 is preferably constituted from glass as the maincomponent, and more preferably crystallized glass having composition ofZnO, B₂O₃, SiO₂ and MnO₂, with ZnO being the main component. Preferablecomposition is 50 to 70% by weight of ZnO, 20 to 30% by weight of B₂O₃,5 to 20% by weight of SiO₂ and 1 to 3% by weight of MnO₂.Crystallization temperature of the glass is around 740° C., and hasthermal expansion coefficient of 4 ppm/° C. This constitution achievesrelatively small difference in thermal expansion between silicon carbideand aluminum nitride that constitute the plate-shaped member 2, andsufficient heat resistance for the wafer heating apparatus 1 used attemperatures not higher than 300° C. Difference in thermal expansionbetween the resistive heating member 5 and the plate-shaped member 2 ispreferably 3.0×10⁻⁶/° C. or less, since it allows the insulation layer60 having substantially lattice configuration to easily absorb thedifference of thermal expansion.

Glass of other compositions including PbO as the main component such asPbO—SiO₂, PbO—B₂O₃—SiO₂ or PbO—ZnO—B₂O₃ includes toxic Pb and a lowcrystallization temperature of 500° C. or lower, and is not preferable.

Thus the wafer heating apparatus 1 is obtained wherein one of theprincipal surfaces of the plate-shaped member 2 serves as the mountingsurface to mount a wafer thereon and the other principal surface has theresistive heating member 5 of one or more circuits formed thereon, whilethe insulation layer 60 having a configuration that corresponds to apart or whole of the resistive heating member 5 is formed.

In the wafer heating apparatus 1, a wafer W can be heated by energizingthe resistive heating member 5 and is cooled down by stopping electricpower to the resistive heating member 5. Cooling operation is preferablycarried out by discharging air as the cooling gas from the nozzle 24thereby cooling the resistive heating member 5 and the plate-shapedceramic member 2. When the cooling gas is blown onto the surfaces havingprotrusions and recesses 55, 61, heat exchange proceeds smoothly betweenthe surfaces having protrusions and recesses 55, 61 and the gas, so asto efficiently cool the plate-shaped ceramic member 2.

The surfaces having protrusions and recesses 55, 61 of lattice-likeconfiguration may be formed on the resistive heating member 5 and/or theinsulation layer 60 by screen printing of a paste prepared from thematerial constituting the resistive heating member 5 and/or theinsulation layer 60. A printing plate for screen printing method ortransfer method may be used. Specifically, the resistive heating member5 and/or the insulation layer 60 of lattice-like configuration may beformed by using a paste prepared from the material constituting theresistive heating member 5 and/or the insulation layer 60 with viscositycontrolled to 3000 poise or more and a mesh printing plate.

The lattice-like configuration may be formed by pressing dimpled jigagainst the resistive heating member 5 and/or the insulation layer 60which has been printed with a smooth surface and has not dried andhardened, so as to transfer the lattice-like configuration onto theprinted surface.

The lattice-like configuration of the resistive heating member 5 and/orthe insulation layer 60 can be completed by firing the printing surfaceat a temperature near the crystallization temperature of the glass.

The glass used to form the insulation layer 60 may be either crystallineor amorphous in nature, and a material having durable temperature of200° C. or higher and difference in thermal expansion coefficient fromthat of the ceramics forming the plate-shaped member 2 is in a rangefrom −5×10⁻⁷/° C. to +5×10⁻⁷/° C. in a temperature range from 0 to 200°C. is preferably used. Use of glass having a value of thermal expansioncoefficient out of the range described above may lead to defects such ascrack and peel-off when cooled down after baking the glass due to largedifference from the thermal expansion coefficient of the ceramics thatforms the plate-shaped member 2.

The insulation layer 60 made of glass may be formed on the plate-shapedceramic member 2 by applying the glass paste by screen printing or thelike, and firing the glass paste at a temperature of 600° C. or higher.

When the insulation layer 60 is made of glass, adhesion of theinsulation layer made of glass and the plate-shaped member 2 made ofsintered body of silicon carbide or sintered aluminum nitride can beimproved by heating the plate-shaped member 2 at a temperature from 850to 1300° C. thereby to oxidize the surface to be covered by theinsulation layer 60.

The resistive heating member 5 and/or the insulation layer 60 may notnecessarily be formed only on the surface of the resistive heatingmember, and may extend to the underlying plate-shaped member 2, and maynot cover the entire surface of the resistive heating member 5. Theresistive heating member 5 and/or the insulation layer 60 may be formedonly on a portion where high stress is generated locally and issusceptible to cracks, such as the portion exposed to the coolingmedium.

Since the overall thickness of the resistive heating member 5 and/or theinsulation layer 60 having the surface having protrusions and recesses55, 61 of substantially lattice configuration is not large, and thestress due to the difference in thermal expansion is mitigated in therecess 57 of the substantially lattice configuration, troubles such ascrack do not occur in the resistive heating member 5 and the insulationlayer 60.

As described above, according to the third embodiment of the presentinvention, it is made possible to provide the wafer heating apparatus ofvery high reliability where the difference in thermal expansion betweenthe plate-shaped member 2, the resistive heating member 5 and/or theinsulation layer 60 is absorbed and deterioration of the resistiveheating member 5 and/or the insulation layer 60 can be suppressed.

The other constitution of the present invention will now be described.

(Plate-Shaped Member 2)

According to the present invention, the plate-shaped member 2 ispreferably formed from a ceramic material having a large value ofYoung's modulus, which deforms less when heated and makes it possible toform a member thinner than in the case of other material. As a result,it is made possible to heat to a predetermined processing temperature ina shorter time and cool down from the processing temperature to the roomtemperature in a shorter time, thus improving the productivity. Jouleheat of the resistive heating member 5 can be transferred quickly with asmaller thickness, and the temperature difference across the mountingsurface 3 can be made extremely small.

In case the plate-shaped member 2 is made of sintered silicon carbide orsintered aluminum nitride, the member deforms less when heated and it ismade possible to form the member thinner. As a result, it is madepossible to heat to a predetermined processing temperature in a shortertime and cool down from the processing temperature to the roomtemperature in a shorter time, thus improving the productivity. Sincethe plate-shaped member 2 has heat conductivity of 10 W/(m·K) or higher,Joule heat of the resistive heating member 5 can be transferred quicklywith a smaller thickness, and the temperature difference across themounting surface 3 can be made extremely small. When heat conductivityis 10 W/(m·K) or lower, it takes a longer time to heat to apredetermined processing temperature and takes a longer time to cooldown from the processing temperature to the room temperature.

Thickness of the plate-shaped member 2 is preferably from 2 to 7 mm.When thickness of the plate-shaped member 2 is less than 2 mm, strengthof the plate-shaped member 2 may become too low to endure the thermalstress when it is heated by the resistive heating member 5 or receivesthe cooling fluid that is blown from the nozzle 24, thus causing cracksin the plate-shaped ceramic member 2 due to the thermal stress caused bythe temperature change. When thickness t is less than 2 mm, it becomesdifficult to smooth out the differences in temperature by means of theplate-shaped ceramic member 2 due to the small thickness, thus resultingin differences in temperature over the mounting surface 3 reflecting thevariation in the Joule heat generated by the resistive heating member 5,thus making it difficult to heat the mounting surface uniformly. Whenthickness of the plate-shaped member 2 is more than 7 mm, heat capacityof, the plate-shaped member 2 becomes large and requires a longer periodof time for the temperature to stabilize after heating or cooling.Specifically, when thickness is more than 7 mm, since the plate-shapedmember 2 has lower heat conductivity than metals even when it is made ofsilicon carbide or aluminum nitride ceramics having high heatconductivity, heat capacity of the plate-shaped member 2 becomes largeand requires a longer period of time to heat to a predeterminedprocessing temperature and takes a longer time to cool down from theprocessing temperature to the room temperature.

When the wafer heating apparatus is used in forming the resist film, itis preferable to use the plate-shaped ceramic member 2 that is made ofsilicon carbide as the main component since this material does notgenerate a gas through reaction with moisture that is contained in theatmosphere or adversely affect the structure of the resist film, thusmaking it possible to form fine wiring in high density. Care should bepaid at this time, so that a sintering assist agent does not includenitrogen that may react with water and form ammonia and/or amine.

Sintered body of silicon carbide that forms the plate-shaped member 2 ismade by mixing silicon carbide as the main component and boron (B) orcarbon (C) as the sintering additive, or adding a metal oxide such asalumina (Al₂O₃) or yttria (Y₂O₃), forming the mixture in plate shapeafter mixing well, and firing the green compact at a temperature from1900 to 2100° C. Silicon carbide based on either a type or β type may beused.

When the sintered body of silicon carbide which has electricconductivity is used as the plate-shaped member 2, the insulation layerthat isolates the plate-shaped member 2 having semi-conductivity and theresistive heating member 5 may be made of glass or a resin. When glassis used, withstanding voltage is below 1.5 kV and sufficient insulationcannot be ensured when the thickness is less than 100 μm. When thethickness is more than 400 μm, on the other hand, cracks may begenerated to make the layer unable to function as an insulation layer,due to large difference in thermal expansion between the insulationlayer and the sintered body of silicon carbide or sintered aluminumnitride that forms the plate-shaped ceramic member 2. Therefore,thickness of the insulation layer made of glass is preferably in a rangefrom 100 to 400 μm, more preferably in a range from 200 to 350 μm.

The principal surface of the plate-shaped member 2 opposite to themounting surface 3 is preferably polished to achieve flatness within 20μm and mean surface roughness (Ra) in a range from 0.1 μm to 0.5 μm, inorder to improve the adhesion of the surface with the insulation layerthat is made of glass or resin.

When the plate-shaped member 2 is made of a sintered material based onaluminum nitride as the main component, an oxide of rare earth elementsuch as Y₂O₃ or Yb₂O₃ and, as required, an oxide of alkali earth metalsuch as CaO are added as the sintering assist agent to the maincomponent of aluminum nitride and, after mixing well and forming intoplate shape, fired at a temperature from 1900 to 2100° C. in nitrogengas atmosphere, so as to obtain satisfactory sintered aluminum nitride.

In order to improve adhesion of the resistive heating member 5 with theplate-shaped member 2, an insulation layer made of glass may be formed,but may be omitted in case sufficient amount of glass is added to theresistive heating member 5 and sufficient bonding strength is obtainedaccordingly.

(Casing 19)

It is preferable that the bottomed metal casing 19 has a depth of 10 to50 mm, with the bottom surface 21 disposed at a distance of 10 to 50 mm,more preferably 20 to 30 mm from the plate-shaped member 2. This makesit easy to equalize the heating of the mounting surface 3 thoughexchange of radiation heat between the plate-shaped member 2 and thebottomed metal casing 19. Also as the effect of thermal insulation withthe outside is provided, time required for the mounting surface 3 toreach stabilized and uniform temperature distribution is reduced.

The resistive heating member 5 is supplied with electric power bypressing the power terminals 11 provided on the bottomed metal casing 19onto the power feeder section 6 formed on the surface of theplate-shaped member 2 by means of an elastic member 8 therebyestablishing electrical continuity. This is because forming theterminals by embedding the terminals made of a metal in the plate-shapedmember 2 adversely affects the uniformity of heating due to the heatcapacity of the terminals. When electrical continuity is established bypressing the power terminals 11 by means of the elastic member as in thepresent invention, thermal stress due to the temperature differencebetween the plate-shaped member 2 and the bottomed metal casing 19 canbe mitigated so as to maintain electrical continuity with highreliability. Moreover, since the contact is prevented from beingconcentrated to a point, an electrically conductive material havingelasticity may be inserted as an intermediate layer. The effect of theintermediate layer can be achieved simply by inserting a foil sheet.Diameter of the power feeder section 6 of the power terminal 11 ispreferably in a range from 1.5 to 5 mm.

(Resistive Heating Member 5)

It is preferable to use a noble metal (for example, metal of Pt group orAu) which has high heat resistance and high oxidization resistance, oran alloy based on such metals as the main component, as the electricallyconductive component of the resistive heating member 5. It is preferablethat the resistive heating member 5 includes 30 to 75% by weight ofglass component, in order to improve adhesion of the resistive heatingmember 5 with the plate-shaped member 2 or the insulation layer 14 andimprove the sintering performance of the resistive heating member 5, andthe resistive heating member 5 has heat conductivity lower than that ofthe plate-shaped member 2.

The resistive heating member 5 may be formed, for example, by printingan electrode paste, which includes electrically conductive metalparticles, glass frit and metal oxide, onto the plate-shaped member 2and baking it. At least one kind of metal selected from among Au, Ag,Cu, Pd, Pt and Rh is preferably used as the metal particles included inthe electrode paste, and the glass frit is preferably a low-expansionglass that is made of an oxide of metal including B, Si and Zn and hasthermal expansion coefficient of 4.5×10⁻⁶/° C. or lower, lower than thatof the plate-shaped member 2. The metal oxide is preferably one kindselected from among silicon oxide, boron oxide, alumina and titania.

The glass frit that forms the resistive heating member 5 is made of anoxide of metal including B, Si and Zn, and the metal particles thatconstitute the resistive heating member 5 have thermal expansioncoefficient higher than that of the plate-shaped ceramic member 2, andtherefore it is preferable to use a low-expansion glass that has thermalexpansion coefficient of 4.5×10⁻⁶/° C. or lower, lower than that of theplate-shaped ceramic member 2, in order to make the thermal expansioncoefficient of the resistive heating member 5 proximate to that of theplate-shaped ceramic member 2.

The reason for using at least one kind selected from among siliconoxide, boron oxide, alumina and titania as the metal oxide that formsthe resistive heating member 5 is that these metal oxides have hightenacity with the metal particles included in the resistive heatingmember 5 and have thermal expansion coefficients proximate to that ofthe plate-shaped member 2, thus showing high tenacity also with theplate-shaped member 2.

It is not desirable, however, that the content of the metal oxide in theresistive heating member 5 exceeds 50%, since resistance of theresistive heating member 5 becomes higher despite increased tenacitywith the plate-shaped member 2. Therefore content of the metal oxide ispreferably not higher than 60%.

The resistive heating member 5 that is made of the electricallyconductive metal particles, the glass frit and the metal oxidepreferably has thermal expansion coefficient of which difference fromthat of the plate-shaped member 2 is not greater than 3.0×10⁻⁶/° C.

This is because it is difficult to constraint the difference in thermalexpansion coefficient between the resistive heating member 5 and theplate-shaped member 2 to 0.1×10⁻⁶/° C. for the reason of themanufacturing process, and a difference in thermal expansion coefficientbetween the resistive heating member 5 and the plate-shaped member 2larger than 3.0×10⁻⁶/° C. may lead to warping of the mounting surface 3in concave shape due to thermal stress generated between the resistiveheating member 5 and the plate-shaped member 2, when the resistiveheating member 5 is energized.

(Nozzles 24 and Arrangement Thereof)

Distance L between the tip of the nozzle 24 and the plate-shaped member2 is important, and is preferably in a range from 0.1 to 10 mm, in orderto blow the cooling gas onto the plate-shaped member 2 at a fasterspeed. Such an arrangement allows the cooling gas discharged from thenozzle to hit the plate-shaped member 2 at a sufficient speed withoutsignificantly slowing down, thus making it possible to efficientlyremove heat.

When distance L between the nozzle 24 and the plate-shaped member 2 isless than 0.1 mm, the gas that has hit the plate-shaped member 2 and hasbounced back hampers the subsequent discharge of the gas, and decreasesthe efficiency of cooling. When distance L between the nozzle 24 and theplate-shaped member 2 is more than 10 mm, the gas diffuses and slowsdown with reduced flow rate when it hits the plate-shaped member 2, thusresulting in lower efficiency of cooling.

Minimum distance between the position of the center of the tip of thenozzle as projected onto the other surface of the plate-shaped member 2and the resistive heating member is preferably from 3 to 10 mm.

In case the minimum distance between the center of the tip of the nozzleand the resistive heating member on the other surface as the plane ofprojection is less than 3 mm, part of the gas discharged from the nozzlehits the surface of the resistive heating member 5. The resistiveheating member 5 includes a glass layer and therefore has low heatconductivity. When heat is transferred from the surface of the resistiveheating member 5 to the plate-shaped member 2, it takes a longer time totransfer the heat because of the existence of the resistive heatinglayer having low heat conductivity and the interface between theresistive heating member 5 and the plate-shaped member 2. Therefore,even when this portion is cooled, the efficiency of cooling is low and along time is taken in cooling.

When the minimum distance between the position of the center of the tipof the nozzle 24 as projected onto the other surface of the plate-shapedmember 2 and the resistive heating member 5 is larger than 10 mm,although the surface area of the plate-shaped member 2 where theresistive heating member 5 is not formed becomes larger and the rate ofcooling becomes faster, surface temperature of the wafer W becomes lowerin a portion thereof that corresponds to the portion of the plate-shapedmember 2 where the resistive heating member 5 is not formed, thusresulting in large temperature difference across the surface of waferand uneven temperature distribution. Therefore, in order to dispose theresistive heating member 5 on of the plate-shaped member 2 and achieveuniform temperature distribution across the wafer W, it is better todecrease the surface area where the resistive heating member 5 is notformed.

In order to ensure sufficient flow velocity of gas required for coolingwith the pressure of a compressor commonly used for cooling gas, orificediameter of the nozzle 24 is preferably in a range from 0.5 to 3 mm.When the orifice diameter of the nozzle 24 is larger than 3.0 mm, flowvelocity becomes too slow and the efficiency of cooling decreasessignificantly. When the orifice diameter is less than 0.5 mm, pressureloss increases and flow velocity becomes slow, efficiency of coolingdecreases. Temperature of the cooling gas was set at the normaltemperature and total flow rate of the cooling gas was set to 120 litersper minute.

The nozzle 24 is preferably disposed at an angle from 80 to 100 degreeswith respect to the plate-shaped member 2. When the angle is set in thisrange, the cooling gas hits the plate-shaped member 2 with strongimpact, thus cooling with high efficiency. When the nozzle 24 isdisposed at an angle less than 80 degrees or larger than 100 degreeswith respect to the plate-shaped member 2, the cooling gas hits theplate-shaped member 2 obliquely and then flows parallel to theplate-shaped member 2, thus resulting in lower efficiency of cooling.

The angle of the nozzle 24 with respect to the plate-shaped member 2refers to the angle between the central axis of the nozzle 24, namelythe flowing direction of the cooling medium, and the plate-shaped member2.

The nozzle 24 is made of a metallic material having resistance againstoxidization such as stainless steel (Fe—Ni—Cr alloy) or nickel (Ni), ora metallic material such as ordinary steel (Fe) or titanium (Ti) platedwith nickel, or plated with nickel and gold thereon, so as to renderoxidization resistance. Ceramic material such as zirconia (ZrO₂) mayalso be preferably used. The nozzle 24 made of such a material enablesit to stabilize the flow velocity as the diameter of the orifice doesnot change due to oxidization when heated, and it is made possible toobtain the wafer heating apparatus having high reliability wherein gasand particulates which are harmful to the heat treatment of the waferwould not be generated.

While impurities such as oil or moisture, should ever mix in the coolinggas, are prevented from damaging the resistive heating member 5 and theinsulation layers 24, 12, it goes without saying that the reliabilitycan be improved further by passing the cooling gas through a filterthereby removing the impurities.

(Opening 16 of Casing)

In the wafer heating apparatus according to the first to thirdembodiment, it is preferable to form the opening 16 occupying 5 to 70%of the area in the base plate 13 of the casing 19, in order to purge thecooling gas to the outside. When the area of the opening 16 is less than5%, the gas discharged from the nozzle 24 and the gas to be purgedbecome mixed in the casing 19, thus decreasing the efficiency ofcooling. When the area of the opening 16 is more than 70%, a space forholding the power terminals 11 and the nozzle 24 cannot be secured,while strength of the casing 19 becomes low and flatness of theplate-shaped member 2 increases, thus resulting in poor uniformity oftemperature in transient condition, particularly during heating.

By providing the opening 16 in the base plate 13, it is made possible toreduce the cooling period as the cooling gas, which has been dischargedfrom the nozzle 24 and has removed heat from the surface of theplate-shaped member 2, is purged through the opening 16 to the outsideof the wafer heating apparatus 1 without remaining within the casing 19,so that the surface of the plate-shaped member 2 can be cooledefficiently by the cooling gas which is subsequently discharged from thenozzle 24.

(Heat Insulating Member 18)

Cross section of the ring-shaped heat insulating member 18 perpendicularto the mounting surface 3 may be of any shape including polygon andcircle. In case the plate-shaped member 2 and the heat insulating member18 make planar contact with each other, heat transfer from theplate-shaped member 2 through the heat insulating 18 to the bottomedmetal casing 19 can be restricted satisfactorily small when width of thecontact region between the plate-shaped member 2 and the heat insulatingmember 18 is in a range from 0.1 mm to 13 mm. The width is morepreferably in a range from 0.1 to 8 mm. If width of the contact regionof the heat insulating member 18 is less than 0.1 mm, the contact regionmay deform when the heat insulating member is put into contact with theplate-shaped member 2, thus causing the heat insulating member 18 tobreak. If width of the contact region of the heat insulating member 18is larger than 13 mm, heat of the plate-shaped member 2 is transferredto the heat insulating member, thus resulting in lower temperature ofthe plate-shaped member 2 along the periphery thereof and difficulty inachieving uniform temperature distribution over the surface of the waferW. Width of the contact region between the plate-shaped member 2 and theheat insulating member 18 is more preferably in a range from 0.1 mm to 8mm, and most preferably from 0.1 to 2 mm.

Heat conductivity of the heat insulating member 18 is preferably lowerthan that of the plate-shaped member 2. When heat conductivity of theheat insulating member 18 is lower than that of the plate-shaped member2, it is made possible to achieve uniform temperature distribution overthe surface of the wafer W that is placed on the plate-shaped member 2,and temperature of the plate-shaped member 2 can be quickly raised andlowered without being affected by the bottomed metal casing 19 due tosmall heat transfer to the heat insulating member 18, thus enabling itto quickly change the temperature.

In the heater 7 where heat conductivity of the heat insulating member 18is less than 10% of the heat conductivity of the plate-shaped member 2,heat transfer from the plate-shaped member to the bottomed metal casing19 decreases and more heat is transferred by the ambient gas (air inthis case) and radiation from the plate-shaped ceramic member to thebottomed metal casing 19.

When heat conductivity of the heat insulating member 18 is higher thanthe heat conductivity of the plate-shaped member 2, heat is transferredfrom the peripheral portion of the plate-shaped member 2 through theheat insulating member 18 to the bottomed metal casing 19, therebyheating the bottomed metal casing 19 while the temperature of theperipheral portion of the plate-shaped member 2 decreases thus resultingin larger temperature difference across the surface of the wafer W. Alsobecause the bottomed metal casing 19 is heated, it takes longer time tocool down the plate-shaped member 2 due to high temperature of the metalcasing 19 when it is attempted to cool down the plate-shaped member 2 byblowing air thereto from the gas nozzle 24, or it takes longer time toheat the plate-shaped member 2 to a predetermined temperature.

The material used to make the heat insulating member 18 preferably hasYoung's modulus of 1 GPa or higher, and more preferably 10 GPa orhigher, in order to maintain a small contact area. Such a level ofcontact area enables it to minimize the deformation of the heatinsulating member 18 even when the plate-shaped member 2 is fastenedonto the bottomed metal casing 19 via the heat insulating member 18having small contact region of 0.1 mm to 8 mm in width. Thus theplate-shaped member 2 can be prevented from being displaced or deviatingfrom parallelism so as to remain held precisely.

The material used to make the heat insulating member 18 is preferably ametal such as carbon steel that includes iron and carbon or a specialsteel that includes nickel, manganese and/or chromium since such metalshave high values of Young's modulus. The material used to make the heatinsulating member 18 also preferably has heat conductivity that is lowerthan that of the plate-shaped member 2, such as stainless steel orFe—Ni—Co alloy, the so-called Koval.

The cross section of the heat insulating member 18 along the planeperpendicular to the mounting surface 3 preferably has circular shaperather than polygon. Use of a wire having circular section 1 mm indiameter as the heat insulating member 18 makes it possible to achieveuniform temperature distribution over the surface of the wafer W andquickly raise and lower the temperature without causing displacement ofthe plate-shaped member 2 and the bottomed metal casing 19. Such aconstitution makes it possible to hold the contact section in stablecondition with a small contact area between the heat insulating member18 and the plate-shaped ceramic member 2 while reducing the possibilityof the contact region being chipped into particles even with a smallcontact area,

One principal surface of the plate-shaped member 2 may have a pluralityof wafer support pins 15 provided thereon as shown in FIG. 1, so as tohold the wafer W at a predetermined distance from the one principalsurface of the plate-shaped member 2. Such a constitution enables it toprevent the temperature from unevenly distributed due to uneven bearing.

Examples of the present invention will now be described.

Examples 1 through 4 are related to the first embodiment, Examples 5 and6 are related to the second embodiment, and Example 7 is related to thethird embodiment, Example 1

A sintered body of silicon carbide having heat conductivity of 100W/(m·K) was ground to make a plurality of round plate-shaped membersmeasuring 3 mm in thickness and 330 mm in diameter.

Then an electrically conductive paste was prepared by mixing Au powderand Pd powder as electrically conductive materials and a glass pastewith a binder of composition described previously. The electricallyconductive paste was printed onto the plate-shaped member in apredetermined pattern of the resistive heating member by screen printingprocess so as to attach the resistive heating member and the powderfeeder section onto the plate-shaped member. After printing, the organicsolvent was evaporated by heating to 150° C., then degreasing treatmentwas applied by heating to 550° C. for 30 minutes, followed by baking ata temperature from 700 to 900° C. Thus the resistive heating memberhaving thickness of 50 μm was made. Composition of the powder feedersection was controlled so as to have specific resistance lower than thatof the resistive heating member, by controlling the proportions of themetallic component and the glass component.

The casing was fastened onto the side wall made of SUS 304 by screwingon the base plate having thickness of 3.0 mm made of SUS 304 as thefoundation.

The plate-shaped member was placed on the casing, and bolts were passedthrough the periphery with nuts screwed thereon while interposing a heatinsulating member and interposing an elastic member on the casing sideso that the plate-shaped member and the casing did not make directcontact with each other, so as to elastically fasten the members andmake the wafer heating apparatus.

Tip of the cooling nozzle of sample No. 1 is in the form of aplate-shaped member (P30 shown in FIG. 3) and is located between theresistive heating member 5 similarly to that shown in FIG. 2 and FIG. 3.Tip of the cooling nozzle of sample No. 2 which is Comparative Exampleis located on the resistive heating member as indicated by P22 shown inFIG. 17 and FIG. 18.

Electric power was supplied to the powder terminals of each of the waferheating apparatuses and the wafer W was kept at 140° C. with temperaturedifference controlled within ±0.5° C. After changing the set temperatureto 90° C., cooling gas was immediately discharged from the nozzle 24toward the plate-shaped member 2. The period of time before thetemperature lowered to 90° C. and temperature difference across thesurface of the wafer W was controlled within ±0.5° C. was defined as thedecreasing temperature stabilization time. In order to improve theefficiency of cooling, target value of decreasing temperaturestabilization time was set to within 200 seconds. Variation intemperature across the surface of the wafer W was evaluated by using atemperature measuring wafer comprising a wafer measuring 300 mm indiameter and temperature sensors embedded therein at 29 positions.

The wafer heating apparatus fabricated was evaluated in a thermostaticchamber that was controlled to 25° C., while flowing the cooling gas setat the normal temperature and total flow rate of 120 liters per minute.Orifice diameter of the nozzle was set to 1.0 mm, and the distance Lbetween the tip of the cooling nozzle and the plate-shaped member wasset to 5.0 mm.

First, the influence of the cooling position on the cooling time wasevaluated, with the results shown in Table 1.

TABLE 1 Decreasing temperature Sample stabilization time No. (seconds) 1Between bands of 195 resistive heating member *2 Resistive heatingmember 300 Sample marked with * is out of the scope of the presentinvention.

In sample No. 1 where the tip of the nozzle was located between thebands of the resistive heating member (P20 in FIG. 3), excellentproperty was obtained with a short temperature stabilization time of 195seconds.

In sample No. 2 of Comparative Example where the tip of the nozzle waslocated above the resistive heating member, the property was not so goodwith a long temperature stabilization time of 300 seconds.

It was found that excellent property with a short cooling time can beachieved when the nozzle tip is a part of the plate-shaped member whichhas a high heat conductivity, This is because the cooling air can beapplied directly to the plate-shaped member having a high heatconductivity so as to remove heat in a shorter time, thereby coolingwith high efficiency. Therefore, it is necessary to cool the part of theplate-shaped member in order to cool with high efficiency.

Example 2

The influence of the distance L between the tip of the nozzle 24 and theplate-shaped member 2 on the cooling time was evaluated, similarly toExample 1 by adjusting the position of securing the nozzle 24 andchanging the distance L between the tip of the nozzle 24 and theplate-shaped member 2.

Electric power was supplied to the powder feeder section 6 of each ofthe wafer heating apparatuses 1 and the surface of the wafer W was keptat 140° C. with temperature difference controlled within ±0.5° C. Afterchanging the set temperature to 90° C., cooling gas was immediatelydischarged from the nozzle 24 toward the plate-shaped member 2. Theperiod of time before the temperature lowered to 90° C. and temperaturedifference across the surface of the wafer W was controlled within ±0.5°C. was defined as the decreasing temperature stabilization time. Inorder to improve the efficiency of cooling, target value of decreasingtemperature stabilization time was set to within 200 seconds. Variationin temperature across the surface of the wafer W was evaluated by usinga temperature measuring wafer comprising a wafer measuring 300 mm indiameter and temperature sensors embedded therein at 29 positions.

The wafer heating apparatus fabricated was evaluated in a thermostaticchamber that was controlled at 25° C., while flowing the cooling gas setat the normal temperature and total flow rate of 120 liters per minute.Orifice diameter of the nozzle 24 was set to 1.0 mm.

The results of evaluation are shown in Table 2.

TABLE 2 Distance (mm) between Decreasing temperature Sample nozzle tipand the plate- stabilization time No. shaped member (mm) (seconds) 30.05 195 4 0.1 190 5 1 185 6 5 185 7 10 190 8 15 195

From Table 2, it can be seen that the distance L between the tip of thecooling nozzle and the plate-shaped member has importance, and thatsamples Nos. 4 through 7 where L is from 0.1 to 10 mm shows excellentproperty with a short temperature stabilization time of 190 seconds orless.

When the distance between the nozzle tip and the plate-shaped member isas small as 0.05 mm or as large as 15 mm as in samples Nos. 3 and 8,however, temperature stabilization time was somewhat longer, 195seconds. In sample No. 3 where the distance L between the plate-shapedmember 2 and the nozzle 24 is as small as 0.05 mm, the gas that has hitthe plate-shaped member 2 and has bounced back hampers the discharge ofthe gas, and decreases the efficiency of cooling. In sample No. 8 wheredistance L between the nozzle 24 and the plate-shaped member 2 is aslarge as 15 mm, the gas diffuses and slows down with reduced flow ratewhen it hits the plate-shaped member 2, thus resulting in lowerefficiency of cooling.

Example 3

Influences on the cooling time were evaluated, similarly to Example 1 byadjusting the position of securing the nozzle 24 and changing theminimum distance between the position of the center of tip of the nozzle24 as projected on the other surface of the plate-shaped member 2 andthe resistive heating member 5.

The results of evaluation are shown in Table 3.

TABLE 3 Minimum distance Temperature (mm) between the differenceDecreasing center of nozzle tip across wafer temperature Sample and theresistive W surface stabilization No. heating member (mm) (° C.) time(seconds) 9 0.1 0.20 185 10 1 0.23 180 11 3 0.23 175 12 10 0.24 170

In samples Nos. 11 through 12 where the minimum distance between theposition of the center of tip of the nozzle 24 as projected on the othersurface of the plate-shaped member 2 and the resistive heating member 5is from 3 to 10 mm, temperature stabilization time was as short as 175seconds or less, and the temperatures across the surface of the wafer Wshowed differences as small as 0.25° C. or less. Thus temperaturestabilization time shorter than that of Example 2 was obtained.

In samples Nos. 9, 10 where the minimum distance between the position ofthe tip of the nozzle 24 as projected on the other surface of theplate-shaped member and the resistive heating member is as small as 0.1and 1 mm, respectively, air discharged from the cooling nozzle 24 hitsthe resistive heating member 5, thus resulting in long temperaturestabilization time. When the air hits the resistive heating member 5, itresults in slow transfer of heat due to the influence of the interfacebetween the resistive heating member 5 having low heat conductivity andthe plate-shaped member 2, thus resulting in low efficiency of coolingand longer cooling time.

From the results described above, it was found that the minimum distancebetween the position of the center of tip of the nozzle 24 as projectedon the other surface of the plate-shaped member and the resistiveheating member 5 has great influence and is preferably 3 mm or more andwithin 100 mm.

Example 4

Influence of the number of nozzles 24 on the cooling time was evaluated,similarly to Example 1 by adjusting the number of nozzles 24. Theresults of evaluation are shown in Table 4.

TABLE 4 Decreasing temperature Sample No. Number of nozzlesstabilization time (seconds) 16 3 170 17 4 165 18 8 160 19 16 160 20 17170

In samples Nos. 17 through 19 where the number of nozzles is from 4 to16, temperature stabilization time was as short as 165 seconds or less,showing favorable results. The temperature stabilization time wasfurther shorter than that of Example 3.

In sample No. 16 where the cooling performance showed unevenness due tosmall number of nozzles, decreasing temperature stabilization time waslong and the efficiency of cooling was low. In sample No. 20, flowvelocity was slow due to a problem related to the facility as the numberof nozzles 24 was 17, thus resulting in longer decreasing temperaturestabilization time and low efficiency of cooling.

When too many nozzles are provided, a large facility having a largecapacity of holding gas is required to obtain sufficient levels of gaspressure and flow velocity required by the nozzles 24, which is notconvenient for mass production. Accordingly, the number of the nozzles24 is preferably from 4 to 16.

Example 5

A sintered body of silicon carbide having heat conductivity of 100W/(m·K) was ground to make a plurality of round plate-shaped membersmeasuring 3 mm in thickness and 330 mm in diameter.

A glass paste was applied to the entire surface on one side of theplate-shaped member by screen printing so as to form an insulation layerwhich was then fired to dry at 150° C., followed by degreasing treatmentwas applied by heating to 550° C. for 30 minutes. Thereafter aninsulation layer was baked at a temperature of 800 to 950° C. Then anelectrically conductive paste was prepared by mixing Au powder and Pdpowder as electrically conductive material and a glass paste with abinder added thereto. The electrically conductive paste was printed ontothe insulation layer in the shape of the resistive heating member shownin FIG. 6, in order to form the resistive heating member and the powderfeeder section. After printing, the organic solvent was evaporated byheating to 150° C., and degreasing treatment was applied by heating to550° C. for 30 minutes, followed by baking at a temperature from 700 to900° C. Thus the resistive heating member having thickness of 55 μm wasformed. Composition of the power feeder section was controlled so as tohave specific resistance lower than that of the resistive heatingmember, by controlling the proportions of the metallic component and theglass component.

Heater section having the insulation layer 12 in band shape so as tocover the resistive heating member, and heater section having theinsulation layer 12 covering the front surface of the resistive heatingmember were made.

The casing was fastened onto the side wall made of SUS 304 by screwingon the base plate having thickness of 3.0 mm made of SUS 304 as thefoundation.

The plate-shaped member was placed on the casing, and bolts were passedthrough the periphery with nuts screwed thereon while interposing a heatinsulating member so that the plate-shaped member and the casing did notmake direct contact with each other, thereby making the wafer heatingapparatus.

Tip of the nozzle of sample No. 101 is at the position of theplate-shaped member (AP in FIG. 7A), and the tip of the nozzle islocated between the resistive heating members 5 similarly to FIG. 8.There is no insulation layer on the resistive heating member.

The same heater section as described above was made, and a paste ofglass frit was printed onto the resistive heating member, and was heatedto form an insulation layer. The insulation layer was formed so as tocorrespond to the resistive heating member zone shown in FIG. 6, whilethe distance of each resistive heating member zone was set to 30 mm forS1, 33 mm for S2 and 42 mm for S3, and the distance between theinsulation layers was accordingly set to 25 mm, 25 mm and 35 mm. Theheat insulating member and the casing were assembled similarly to thatdescribed above, thereby making the wafer heating apparatus havingnozzles provided thereon.

The tip of the nozzle of sample No. 102 is located between the resistiveheating members. Insulation layers are also formed to cover thering-shaped zones individually on the resistive heating member (FIG. 9).Distance between the insulation layer that covers the outermostresistive heating member zone and the insulation layer that covers theinnermost resistive heating member zone is set to 35 mm, and the tip ofthe nozzle was disposed between the insulation layers.

The tip of the nozzle of sample No. 103 is located between the resistiveheating members. Insulating layer is uniformly formed over the entiresurface of the resistive heating member (FIG. 10).

In sample No. 104, the nozzle was located on the insulation layer of theoutermost resistive heating member zone.

Orifice diameter at the tip of the nozzle was 1.2 mm, and the distancebetween the nozzle tip and the heater section was 6 mm. Samples Nos. 101through 104 were provided with 8 nozzles disposed on the outside and 4nozzles disposed on the ring-shaped resistive heating member zone 4 atthe second position from the center of the plate-shaped member.

Electric power was supplied to the powder terminals of each of the waferheating apparatuses and the surface of the wafer W was kept at 140° C.with temperature difference controlled within ±0.5° C. After changingthe set temperature to 90° C., cooling gas was immediately dischargedfrom all of the nozzles. The period of time before the temperaturelowered to 90° C. and temperature difference across the surface of thewafer W was controlled within ±0.5° C. was defined as the cooling time.In order to improve the efficiency of cooling, target value ofdecreasing temperature stabilization time was set to within 180 seconds.Variation in temperature across the surface of the wafer W was evaluatedby using a temperature measuring wafer comprising a wafer measuring 300mm in diameter and temperature sensors embedded therein at 29 positions.

The wafer heating apparatus fabricated as described above was evaluatedin a thermostatic chamber that was controlled at 25° C., while causingthe cooling gas of the normal temperature to flow at total flow rate of120 liters per minute.

Influence of the cooling position on the cooling time was evaluated.

After raising the temperature of the wafer heating apparatus from 30 to200° C. in 5 minutes and holding this temperature for 5 minutes,forcible cooling operation was carried out for 30 minutes to completeone heating and cooling cycle. This cycle was repeated 1000 times. Thenthe temperature was changed from the room temperature to 200° C., andthe difference between the maximum temperature and minimum temperatureof the wafer was determined 10 minutes later, as the temperaturedifference in stationary wafer W.

The results are sown in Table 5.

TABLE 5 Temperature difference in wafer of stationary Cooling conditionafter Sample Position of nozzle Form of insulation time repetitiveheating and No. tip layer 12 (seconds) cooling cycles (° C.) 101 Oninsulation layer Not provided 135 0.32 14 of plate-shaped member betweenresistive heating members 102 On insulation layer The resistive heating140 0.24 14 of plate-shaped member is covered by member betweenband-shaped insulation resistive heating layer 12. members 103 Oninsulation layer Insulation layer is 152 0.25 12 of plate-shapedprovided over the member between entire surface to cover resistiveheating the resistive heating members member. *104 On insulation layerInsulation layer is 358 0.32 12 and on resistive provided over theheating member entire surface to cover the resistive heating member.Marked with * is an example out of the scope of the present invention.

Sample No. 101 where the tip of the nozzle is located between the bandsof resistive heating members (AP in FIG. 7A) showed excellent propertieswith short cooling time of 135 seconds and small temperature differencein stationary wafer W of 0.32° C. after heating and cooling cycles.

Sample No. 102 where the band-shaped insulation layer is located on theresistive heating member showed satisfactory properties with shortcooling time of 140 seconds and small temperature difference instationary wafer W of 0.24° C. after heating and cooling cycles.

Sample No. 103, where the insulation layer 14 was formed on theplate-shaped member and the resistive heating member was formed thereon,with an insulation layer formed further on the resistive heating member,and the heater section was cooled by applying the cooling gas to theinsulation layer located between the resistive heating members, showedshort cooling time of 152 seconds, small temperature difference instationary wafer W of 0.25° C. after heating and cooling cycles and highdurability.

It was found that excellent properties with short cooling time can beachieved by arranging so that the tip of the nozzle as projected ontothe other surface of the plate-shaped member whereon the resistiveheating member is formed is located between the resistive heatingmembers where heat can be transferred easily to the plate-shaped member,and cooling the plate-shaped member via the insulation layer.

Sample No. 104, where the insulation layer was formed on the resistiveheating member and the resistive heating member was formed thereon, withan insulation layer formed further on the resistive heating member, andthe cooling gas was blown onto the insulation layer located on theresistive heating member for cooling, showed long cooling time of 358seconds.

Example 6

In Example 6, samples were made similarly to samples Nos. 101 through103 of Example 5, surfaces of the insulation layers were processed bysand blast into surface having protrusions and recesses, thereby makingsamples Nos. 121 through 124. The grooves were formed with width of 30μm and depth of 20 μm and the protrusions were formed in square shapemeasuring 40 μm on one side. The samples were evaluated similarly toExample 5.

The results are sown in Table 6.

TABLE 6 Whether the insulation layer 12 has surface having CoolingSample Position of nozzle Form of insulation layer protrusions and timeNo. tip 12 recesses or not (seconds) 121 On insulation layer Notprovided Yes 95 14 of plate-shaped member between resistive heatingmembers 122 On insulation layer The resistive heating Yes 102 14 ofplate-shaped member is covered by member between band-shaped insulationresistive heating layer 12. members 123 On insulation layer Insulatinglayer is Yes 108 12 of plate-shaped provided over the entire memberbetween surface to cover the resistive heating resistive heating membersmember. Samples Nos. 121 through 123 showed cooling time of 95, 102 and108 seconds, respectively, far shorter than 135, 140 and 152 seconds ofsamples Nos. 101 through 103, indicating that excellent coolingperformance is obtained by providing surface having protrusions andrecesses of the insulation layer.

Example 7

Examples and Comparative Examples of the present invention will now bedescribed (members common to Examples and Comparative Examples may bedenoted by either of the reference numerals used therefore).

A sintered body of aluminum nitride having heat conductivity of 100W/(m·K), specific gravity of 3.2 and water absorption of 0% was groundto make a plurality of round plate-shaped members 2 measuring 300 mm indiameter while changing the thickness.

A paste formed by mixing Pt, Au, Ag and glass powders was printed in thepattern of the resistive heating member 5 by screen printing method onthe plate-shaped member 2, so as to form the resistive heating member 5on the plate-shaped member 2. Since the paste was prepared to have veryhigh fluidity with viscosity of about 100 poise for the purpose ofmaking the printing process easier, the surfaces having protrusions andrecesses 55, 61 were smoothed out after printing, thus resulting in verysmooth printed surface regardless of the mesh size of the printingplate.

Before the printed surface dried completely, dimpled jigs having varioussizes were thereon so as to transfer substantially latticeconfiguration. Since the resistive heating member 5 had low consistencyin the configuration thereof immediately after being printed, thesubstantially lattice configuration could not be transferred, while theresistive heating member 5 which had completely dried was too hard to besubjected to transferring.

In case the resistive heating member 5 was dried at 80° C. for about 10minutes after printing, the substantially lattice configuration could betransferred. Then the plate-shaped member 2, with the resistive heatingmember 5 having the surface having protrusions and recesses 55, 61 ofsubstantially lattice configuration was formed thereon, was fired at700° C., near the crystallization temperature of glass, so as to obtainthe resistive heating member 5 having various properties shown in Table7.

Since the resistive heating member 5 shows shrinkage of severalpercentage points when fired, dimpled jig having such a size selected bytaking account of the shrinkage ratio was used.

While the process described above employed the method of transferringthe substantially lattice configuration by means of the dimpled jig, itwas also possible to form the substantially lattice configuration byusing the mesh of the printing plate, used in the screen printingprocess. Specifically, it was possible to form the surface havingprotrusions and recesses having 0.2 to 80 grooves per 1 mm of widthformed in lattice shape, although the ease of printing was somewhatinferior, by printing using a printing plate having mesh of 40 to 600according to JIS R6002 and a paste having very high viscosity of about3000 poise and high consistency of configuration to form the resistiveheating member, then drying and firing the printed layer whereon thepattern of the printing plate remained. Width of the grooves could bechanged simply by changing the mesh size. The method of forming thesubstantially lattice configuration by using the mesh of the printingplate used in the screen printing process has an advantage ofsimplifying the process since the dimpled jig is unnecessary. Since thepaste of the resistive heating member 5 shows shrinkage of severalpercentage points when fired, mesh size is selected by taking account ofthe shrinkage ratio was used.

Then the insulation layer 60, with the resistive heating member 5 havingthe surfaces having protrusions and recesses 55, 61 of substantiallylattice configuration formed thereon, was formed. As the method forforming the insulation layer 60, with the resistive heating member 5which had the surfaces having protrusions and recesses 55, 61 ofsubstantially lattice configuration formed thereon, a glass pasteprepared by mixing a glass powder, ethyl cellulose as a binder andterpineol as an organic solvent was printed smoothly by screen printingmethod. Before the glass paste was dried completely, dimpled jigs havingvarious sizes were thereon so as to transfer substantially latticeconfiguration. Then the plate-shaped member 2, with the resistiveheating member 5 having the insulation layer 60 with the substantiallylattice configuration formed thereon, was fired at 700° C., near thecrystallization temperature of glass, so as to obtain the insulationlayer 60 of substantially lattice configuration.

Since the glass paste also shows shrinkage of several percentage pointswhen fired, dimpled jig having such a size selected by taking account ofthe shrinkage ratio was used.

While the process described above employed the method of transferringthe substantially lattice configuration by means of the dimpled jig, itwas also possible to form the substantially lattice configuration byusing the mesh of the printing plate used in the screen printingprocess. Specifically, it was possible to form the surface havingprotrusions and recesses having 0.2 to 80 grooves per 1 mm of widthformed in lattice shape, although the ease of printing was somewhatinferior, by using printing plate having mesh of 40 to 600 according toJIS R6002.

It goes without saying that width of the grooves can be changed simplyby changing the mesh size according to the desired latticeconfiguration. The method of forming the substantially latticeconfiguration by using the mesh of the printing plate used in the screenprinting process has an advantage of simplifying the process since thedimpled jig is unnecessary. Since the glass paste shows shrinkage ofseveral percentage points when fired, mesh size is selected by takingaccount of the shrinkage ratio may be used.

The plate-shaped member 2 described above and the casing 19 wereassembled, thereby making the wafer heating apparatus 1.

Heating and cooling cycle test was conducted by repeating the cyclewhere, with 200 V applied to the wafer heating apparatus, temperaturewas raised to 300° C., the cooling medium was purged through thedischarge port, and the temperature was lowered quickly from 300° C. tothe room temperature. The relation between the number of heating andcooling cycles and peel-off or crack of the resistive heating member 5was investigated.

In the first heating and cooling cycle, the period of time taken tolower the temperature from 300° C. to 50° C. was measured as the coolingtime.

The results are shown in Table 7 (Tables 7-1 through 7-6).

TABLE 7-1 Sample Surface configuration of Surface configuration of No.resistive heating member insulation layer *201 Smooth Smooth 202 SmoothGrooves of substantially lattice configuration 203 Grooves ofsubstantially Smooth lattice configuration 204 Surface havingprotrusions Surface having and recesses protrusions and recesses 205Grooves of substantially Grooves of substantially lattice configurationlattice configuration 206 Grooves of substantially Grooves ofsubstantially lattice configuration lattice configuration 207 Grooves ofsubstantially Grooves of substantially lattice configuration latticeconfiguration 208 Grooves of substantially Grooves of substantiallylattice configuration lattice configuration 209 Grooves of substantiallyGrooves of substantially lattice configuration lattice configuration 210Grooves of substantially Grooves of substantially lattice configurationlattice configuration 211 Grooves of substantially Grooves ofsubstantially lattice configuration lattice configuration 212 Grooves ofsubstantially Grooves of substantially lattice configuration latticeconfiguration 213 Grooves of substantially Grooves of substantiallylattice configuration lattice configuration 214 Grooves of substantiallyGrooves of substantially lattice configuration lattice configuration 215Grooves of substantially Grooves of substantially lattice configurationlattice configuration 216 Grooves of substantially Grooves ofsubstantially lattice configuration lattice configuration 217 Grooves ofsubstantially Grooves of substantially lattice configuration latticeconfiguration 218 Grooves of substantially Grooves of substantiallylattice configuration lattice configuration 219 Grooves of substantiallyGrooves of substantially lattice configuration lattice configuration 220Grooves of substantially Grooves of substantially lattice configurationlattice configuration 221 Grooves of substantially Grooves ofsubstantially lattice configuration lattice configuration 222 Grooves ofsubstantially Grooves of substantially lattice configuration latticeconfiguration 223 Grooves of substantially Grooves of substantiallylattice configuration lattice configuration 224 Grooves of substantiallyGrooves of substantially lattice configuration lattice configuration 225Grooves of substantially Grooves of substantially lattice configurationlattice configuration 226 Grooves of substantially Grooves ofsubstantially lattice configuration lattice configuration 227 Grooves ofsubstantially Grooves of substantially lattice configuration latticeconfiguration 228 Grooves of substantially Grooves of substantiallylattice configuration lattice configuration 229 Grooves of substantiallyGrooves of substantially lattice configuration lattice configuration 230Grooves of substantially Grooves of substantially lattice configurationlattice configuration 231 Grooves of substantially Grooves ofsubstantially lattice configuration lattice configuration Marked with *is an example out of the scope of the present invention.

TABLE 7-2 Resistive heating member Number of Thickness Thickness (tp)Mean thickness of Sample lattice-shaped (tv) of of protrusion Proportionresistive heating No. grooves per 1 mm recess (μm) (μm) (tp/tv) × 100member (μm) *201 2 202 2 203 20 25 35 140.0% 60 204 25 35 60 205 0.1 2535 140.0% 60 206 0.2 25 35 140.0% 60 207 0.4 25 35 140.0% 60 208 40 2535 140.0% 60 209 80 25 35 140.0% 60 210 100 25 35 140.0% 60 211 20 1 1100.0% 2 212 20 25 27 108.0% 52 213 20 25 35 140.0% 60 214 20 18 35194.4% 53 215 20 1 2 200.0% 3 216 20 17 35 205.9% 52 217 20 25 45 180.0%70 218 20 25 35 140.0% 60 219 20 25 35 140.0% 60 220 20 25 35 140.0% 60221 20 25 35 140.0% 60 222 20 25 35 140.0% 60 223 20 25 35 140.0% 60 22420 25 35 140.0% 60 225 20 25 35 140.0% 60 226 20 25 35 140.0% 60 227 2025 35 140.0% 60 228 20 25 35 140.0% 60 229 20 25 35 140.0% 60 230 20 2535 140.0% 60 231 20 25 35 140.0% 60

TABLE 7-3 Insulation layer Number of Thickness Thickness (tp) Meanthickness Sample lattice-shaped (tv) of of protrusion Proportion ofinsulation No. grooves per 1 mm recess (μm) (μm) (tp/tv) × 100 layer(μm) *201 2 202 20 25 35 140.0% 60 203 2 204 2 205 0.1 25 35 140.0% 60206 0.2 25 35 140.0% 60 207 0.4 25 35 140.0% 60 208 40 25 35 140.0% 60209 80 25 35 140.0% 60 210 100 25 35 140.0% 60 211 20 1 1 100.0% 2 21220 25 27 108.0% 52 213 20 25 35 140.0% 60 214 20 18 35 194.4% 53 215 201 2 200.0% 3 216 20 17 35 205.9% 52 217 20 25 45 180.0% 70 218 20 25 35140.0% 60 219 20 25 35 140.0% 60 220 20 25 35 140.0% 60 221 20 25 35140.0% 60 222 20 25 35 140.0% 60 223 20 25 35 140.0% 60 224 20 25 35140.0% 60 225 20 25 35 140.0% 60 226 20 25 35 140.0% 60 227 20 25 35140.0% 60 228 20 25 35 140.0% 60 229 20 25 35 140.0% 60 230 20 25 35140.0% 60 231 20 25 35 140.0% 60

TABLE 7-4 Composition of resistive heating member (% by weight) SampleNo. Pt Au Ag Glass *201 30 20 0 50 202 30 20 0 50 203 30 20 0 50 204 3020 0 50 205 30 20 0 50 206 30 20 0 50 207 30 20 0 50 208 30 20 0 50 20930 20 0 50 210 30 20 0 50 211 30 20 0 50 212 30 20 0 50 213 30 20 0 50214 30 20 0 50 215 30 20 0 50 216 30 20 0 50 217 30 20 0 50 218 30 20 050 219 30 20 0 50 220 30 20 0 50 221 40 10 0 50 222 30 20 0 50 223 20 300 50 224 40 0 10 50 225 30 0 20 50 226 20 0 30 50 227 0 20 30 50 228 030 30 40 229 0 30 20 50 230 0 10 40 50 231 10 20 10 60

TABLE 7-5 Composition of insulation layer (% by weight) Sample No. ZnOB₂O₃ SiO₂ MnO₂ *201 50 30 20 0 202 50 30 20 0 203 50 30 20 0 204 50 3020 0 205 50 30 20 0 206 50 30 20 0 207 50 30 20 0 208 50 30 20 0 209 5030 20 0 210 50 30 20 0 211 50 30 20 0 212 50 30 20 0 213 50 30 20 0 21450 30 20 0 215 50 30 20 0 216 50 30 20 0 217 50 30 20 0 218 50 30 18 2219 60 20 18 2 220 70 20 8 2 221 50 30 20 0 222 60 20 18 2 223 50 30 200 224 50 30 20 0 225 60 20 18 2 226 50 30 20 0 227 50 30 20 0 228 50 3020 0 229 50 30 20 0 230 50 30 20 0 231 50 30 20 0

TABLE 7-6 Number of heating and Cooling time (time taken Sample coolingcycles before to cool from 300° C. to No. crack 50° C.) (seconds) *2012400 450 202 4050 300 203 4060 300 204 4100 300 205 5500 280 206 9200270 207 14300 260 208 14600 220 209 9200 220 210 6800 220 211 4200 220212 14800 220 213 15000 220 214 14800 220 215 11000 220 216 9800 220 2176000 220 218 15400 220 219 23200 220 220 15600 220 221 12300 220 22223200 220 223 11200 220 224 12300 220 225 23200 220 226 11200 220 22713400 220 228 13500 220 229 13100 220 230 13500 220 231 8800 220

Samples Nos. 202 through 231 of the wafer heating apparatus 1, where theresistive heating member 5 and/or the insulation layer 60 had surfaceshaving protrusions and recesses 55, 61 such as substantially latticeconfiguration formed thereon, showed satisfactory performance withoutpeel-of or crack of the resistive heating member 5 after undergoing 4000heating and cooling cycles.

The wafer heating apparatus 1 having the resistive heating member 5 ofsmooth surface as sample No. 201 experienced crack in the resistiveheating member 5 after 400 heating and cooling cycles.

Samples Nos. 206 through 209 of the wafer heating apparatus 1, where theresistive heating member 5 and/or the insulation layer 60 of theplate-shaped member 2 had surface having protrusions and recesses 55, 61of substantially lattice configuration formed thereon, and had 0.2 to 80grooves per 1 mm of width formed in lattice shape, provided the waferheating apparatus 1 of high reliability where the difference in thermalexpansion between the plate-shaped member 2, the resistive heatingmember 2 and/or the insulation layer 60 was absorbed and deteriorationof the resistive heating member 5 and/or the insulation layer 60 couldbe suppressed, thus resulting in high durability of 9000 cycles withoutpeel-of or crack of the resistive heating member 5.

Samples Nos. 212 through 215 where the surface having protrusions andrecesses 55, 61 had the proportion (tp/tv)×100 of the thickness (tp) ofthe protrusion to the thickness (tv) of the recess in a range from 105to 2000, and mean thickness of the resistive heating member 5 or theinsulation layer 60 was in a range from 3 to 60 μm, showed even higherdurability of 10000 cycles without peel-of or crack.

Thus the wafer heating apparatus 1 of particularly high reliability wasobtained.

Samples Nos. 202 through 231, where the resistive heating member 5and/or the insulation layer 60 had surface having protrusions andrecesses 55, 61, showed cooling time of 300 seconds or less, shorterthan that of sample No. 201 that was Comparative Example without surfacehaving protrusions and recesses 55, 61, while the cooling time wasshorter when surface having protrusions and recesses 55, 61,particularly grooves of substantially lattice configuration were formed.

As for the glass component, crystallized glass based onZnO—B₂O₃—SiO₂—MnO₂ including ZnO as the main component showed goodresults. Particularly, samples Nos. 218 through 220, where theinsulation layer was formed from glass having composition of 50 to 70%by weight of ZnO, 20 to 30% by weight of B₂O₃, 5 to 20% by weight ofSiO₂ and 1 to 2% by weight of MnO₂ showed satisfactory results byenduring the largest number of heating and cooling cycles from 15000 to232000.

The resistive heating member 5 formed from a material consisting of atleast two materials selected from among Pt, Au and Ag and glass showedgood results, particularly when the composition was 30% of Pt, 20% of Auand 50% by weight of glass, or 30% of Pt, 20% of Ag and 50% by weight ofglass.

It yielded better results to keep the errors of these values within ±5%by weight.

The insulation layer 60 may not necessarily be formed only on thesurface of the resistive heating member 5, and may extend to theunderlying plate-shaped member 2 without causing any problem.

1-21. (canceled)
 22. A wafer heating apparatus comprising: a base member comprising a first surface configured for mounting a wafer and a second surface; resistive heating members on the second surface, each resistive heating member having a surface which comprises protrusions and recesses; and a nozzle configured to cool the base member, the nozzle having a tip facing a portion of the second surface located between the resistive heating members.
 23. The wafer heating apparatus according to claim 22, wherein the protrusions and recesses are disposed regularly.
 24. The wafer heating apparatus according to claim 22, wherein the protrusions and recesses are grooves of lattice-like configuration.
 25. The wafer heating apparatus according to claim 23, wherein the number of the grooves is not less than 0.2 and not more than 80 per 1 mm of the width of the surface of the resistive heating member in the lattice array direction.
 26. The wafer heating apparatus according to claim 22, wherein a mean thickness of the resistive heating member is not less than 3 micron and not more than 60 micron.
 27. The wafer heating apparatus according to claim 22, wherein the proportion (tp/tv)*100 is not less than 105% and not more than 200% when the thickness of the protrusion is represented as tp and the thickness of the recess is represented as tv.
 28. The wafer heating apparatus according to claim 22, wherein a mean thickness of the resistive heating member is not less than 3 micron and not more than 60 micron, and wherein the proportion (tp/tv)*100 is not less than 105% and not more than 200% when the thickness of the protrusion is represented as tp and the thickness of the recess is represented as tv.
 29. The wafer heating apparatus according to claim 22, wherein a width of the protrusion is substantially equal to a width of the recess.
 30. The wafer heating apparatus according to claim 22, further comprising an insulation layer on the resistive heating member.
 31. The wafer heating apparatus according to claim 30, wherein the insulation layer has a surface comprising protrusions and recesses.
 32. The wafer heating apparatus according to claim 31, wherein the protrusions and recesses of the insulation layer are grooves of lattice-like configuration.
 33. The wafer heating apparatus according to claim 30, wherein a mean thickness of the insulation layer is not less than 3 micron and not more than 60 micron.
 34. The wafer heating apparatus according to claim 30, wherein the proportion (Tp/Tv)*100 is not less than 105% and not more than 200% when the thickness of the protrusion of the insulation layer is represented as Tp and the thickness of the recess of the insulation layer is represented as Tv.
 35. The wafer heating apparatus according to claim 30, wherein a mean thickness of the insulation layer is not less than 3 micron and not more than 60 micron, and wherein the proportion (Tp/Tv)*100 is not less than 105% and not more than 200% when the thickness of the protrusion of the insulation layer is represented as Tp and the thickness of the recess of the insulation layer is represented as Tv.
 36. The wafer heating apparatus according to claim 30, wherein a width of the protrusion and a width of the recess of the heating member is substantially equal to that of the insulation layer, respectively.
 37. The wafer heating apparatus according to claim 22, further comprising: a power feeder terminal configured to supply electric power to the resistive heating member; and a casing surrounding the power feeder terminal.
 38. The wafer heating apparatus according to claim 22, wherein the resistive heating member comprises a glass and at least two selected from among Pt, Au and Ag.
 39. The wafer heating apparatus according to claim 28, wherein a thickness of the base member is not less than 2 mm and not more than 7 mm.
 40. A wafer heating apparatus comprising: a base member comprising a first surface configured for mounting a wafer and a second surface; resistive heating members on the second surface; an insulation layer on each of the resistive heating members, wherein each of the resistive heating members has a surface which comprises protrusions and recesses; and a nozzle configured for cooling the base member, the nozzle having a tip facing a portion of the second surface located between the resistive heating members. 